Induction of labour at or beyond 37 weeks' gestation

Philippa Middleton; Emily Shepherd; Jonathan Morris; Caroline A Crowther; Judith C Gomersall

doi:10.1002/14651858.CD004945.pub5

. 2020 Jul 15;2020(7):CD004945. doi: 10.1002/14651858.CD004945.pub5

Induction of labour at or beyond 37 weeks' gestation

Philippa Middleton ^1,^✉, Emily Shepherd ^1,², Jonathan Morris ³, Caroline A Crowther ⁴, Judith C Gomersall ⁵

Editor: Cochrane Pregnancy and Childbirth Group

PMCID: PMC7389871 PMID: 32666584

Abstract

Background

Risks of stillbirth or neonatal death increase as gestation continues beyond term (around 40 weeks' gestation). It is unclear whether a policy of labour induction can reduce these risks. This Cochrane Review is an update of a review that was originally published in 2006 and subsequently updated in 2012 and 2018.

Objectives

To assess the effects of a policy of labour induction at or beyond 37 weeks' gestation compared with a policy of awaiting spontaneous labour indefinitely (or until a later gestational age, or until a maternal or fetal indication for induction of labour arises) on pregnancy outcomes for the infant and the mother.

Search methods

For this update, we searched Cochrane Pregnancy and Childbirth’s Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (17 July 2019), and reference lists of retrieved studies.

Selection criteria

Randomised controlled trials (RCTs) conducted in pregnant women at or beyond 37 weeks, comparing a policy of labour induction with a policy of awaiting spontaneous onset of labour (expectant management). We also included trials published in abstract form only. Cluster‐RCTs, quasi‐RCTs and trials using a cross‐over design were not eligible for inclusion in this review.

We included pregnant women at or beyond 37 weeks' gestation. Since risk factors at this stage of pregnancy would normally require intervention, only trials including women at low risk for complications, as defined by trialists, were eligible. The trials of induction of labour in women with prelabour rupture of membranes at or beyond term were not considered in this review but are considered in a separate Cochrane Review.

Data collection and analysis

Two review authors independently assessed trials for inclusion, assessed risk of bias and extracted data. Data were checked for accuracy. We assessed the certainty of evidence using the GRADE approach.

Main results

In this updated review, we included 34 RCTs (reporting on over 21,000 women and infants) mostly conducted in high‐income settings. The trials compared a policy to induce labour usually after 41 completed weeks of gestation (> 287 days) with waiting for labour to start and/or waiting for a period before inducing labour. The trials were generally at low to moderate risk of bias.

Compared with a policy of expectant management, a policy of labour induction was associated with fewer (all‐cause) perinatal deaths (risk ratio (RR) 0.31, 95% confidence interval (CI) 0.15 to 0.64; 22 trials, 18,795 infants; high‐certainty evidence). There were four perinatal deaths in the labour induction policy group compared with 25 perinatal deaths in the expectant management group. The number needed to treat for an additional beneficial outcome (NNTB) with induction of labour, in order to prevent one perinatal death, was 544 (95% CI 441 to 1042). There were also fewer stillbirths in the induction group (RR 0.30, 95% CI 0.12 to 0.75; 22 trials, 18,795 infants; high‐certainty evidence); two in the induction policy group and 16 in the expectant management group.

For women in the policy of induction arms of trials, there were probably fewer caesarean sections compared with expectant management (RR 0.90, 95% CI 0.85 to 0.95; 31 trials, 21,030 women; moderate‐certainty evidence); and probably little or no difference in operative vaginal births with induction (RR 1.03, 95% CI 0.96 to 1.10; 22 trials, 18,584 women; moderate‐certainty evidence). Induction may make little or difference to perineal trauma (severe perineal tear: RR 1.04, 95% CI 0.85 to 1.26; 5 trials; 11,589 women; low‐certainty evidence). Induction probably makes little or no difference to postpartum haemorrhage (RR 1.02, 95% CI 0.91 to 1.15, 9 trials; 12,609 women; moderate‐certainty evidence), or breastfeeding at discharge (RR 1.00, 95% CI 0.96 to 1.04; 2 trials, 7487 women; moderate‐certainty evidence). Very low certainty evidence means that we are uncertain about the effect of induction or expectant management on the length of maternal hospital stay (average mean difference (MD) ‐0.19 days, 95% CI ‐0.56 to 0.18; 7 trials; 4120 women; Tau² = 0.20; I² = 94%).

Rates of neonatal intensive care unit (NICU) admission were lower (RR 0.88, 95% CI 0.80 to 0.96; 17 trials, 17,826 infants; high‐certainty evidence), and probably fewer babies had Apgar scores less than seven at five minutes in the induction groups compared with expectant management (RR 0.73, 95% CI 0.56 to 0.96; 20 trials, 18,345 infants; moderate‐certainty evidence).

Induction or expectant management may make little or no difference for neonatal encephalopathy (RR 0.69, 95% CI 0.37 to 1.31; 2 trials, 8851 infants; low‐certainty evidence, and probably makes little or no difference for neonatal trauma (RR 0.97, 95% CI 0.63 to 1.49; 5 trials, 13,106 infants; moderate‐certainty evidence) for induction compared with expectant management. Neurodevelopment at childhood follow‐up and postnatal depression were not reported by any trials.

In subgroup analyses, no differences were seen for timing of induction (< 40 versus 40‐41 versus ≥ 41 weeks' gestation), by parity (primiparous versus multiparous) or state of cervix for any of the main outcomes (perinatal death, stillbirth, NICU admission, caesarean section, operative vaginal birth, or perineal trauma).

Authors' conclusions

There is a clear reduction in perinatal death with a policy of labour induction at or beyond 37 weeks compared with expectant management, though absolute rates are small (0.4 versus 3 deaths per 1000). There were also lower caesarean rates without increasing rates of operative vaginal births and there were fewer NICU admissions with a policy of induction. Most of the important outcomes assessed using GRADE had high‐ or moderate‐certainty ratings.

While existing trials have not yet reported on childhood neurodevelopment, this is an important area for future research.

The optimal timing of offering induction of labour to women at or beyond 37 weeks' gestation needs further investigation, as does further exploration of risk profiles of women and their values and preferences. Offering women tailored counselling may help them make an informed choice between induction of labour for pregnancies, particularly those continuing beyond 41 weeks ‐ or waiting for labour to start and/or waiting before inducing labour.

Plain language summary

Induction of labour in women with normal pregnancies at or beyond 37 weeks

Does a policy of inducing labour at or beyond 37 weeks' gestation reduce risks for babies and their mothers when compared with a policy of waiting until a later gestational age, or until there is an indication for induction of labour?

This review was originally published in 2006 and subsequently updated in 2012 and 2018.

What is the issue?

The average pregnancy lasts 40 weeks from the start of the woman's last menstrual period. Pregnancies continuing beyond 42 weeks are described as 'post‐term' or 'postdate' and a woman and her clinician may decide to bring the birth on by induction. Factors associated with post‐term birth include obesity, first baby and the mother being more than 30 years old.

Why is this important?

Prolonged gestation may increase risks for babies, including a greater risk of death (before or shortly after birth). However, inducing labour may also have risks for mothers and their babies, especially if the women’s cervix is not ready to go into labour. Current tests cannot predict the risks for babies or their mother, as such, and many hospitals have policies for how long pregnancies should be allowed to continue.

What evidence did we find?

We searched for evidence (17 July 2019) and identified 34 randomised controlled trials based in 16 different countries and involving > 21,500 women (mostly with low risk of complications). The trials compared a policy of inducing labour usually after 41 completed weeks of gestation (> 287 days) with a policy of waiting (expectant management).

A policy of labour induction was associated with fewer perinatal deaths (22 trials, 18,795 infants). Four perinatal deaths occurred in the labour induction policy group compared with 25 perinatal deaths in the expectant management group. Fewer stillbirths occurred in the induction group (22 trials, 18,795 infants), with two in the induction policy group and 16 in the expectant management group.

Women in the induction arms of the trials were probably less likely to have a caesarean section compared with expectant management (31 trials, 21,030 women) and there was probably little or no difference in assisted vaginal births (22 trials, 18,584 women).

Fewer babies went into the neonatal intensive care unit (NICU) in the policy of labour induction group (17 trials, 17,826 infants; high‐certainty evidence). A simple test of the baby’s health (Apgar score) at five minutes was probably more favourable in the induction groups compared with expectant management (20 trials, 18,345 infants).

A policy of induction may make little or no difference to the women experiencing perineal trauma and probably makes little or no difference to the number of women having a postpartum haemorrhage, or breastfeeding at discharge. We are uncertain about the effect of induction or expectant management on the length of maternal hospital stay due to very low‐certainty evidence.

For newborn babies, the number with trauma or encephalopathy were similar in the induction and expectant management groups (moderate and low‐certainty evidence respectively). Neurodevelopment at childhood follow‐up and postnatal depression were not reported in any of the trials. Only three trials reported some measure of maternal satisfaction.

What does this mean?

A policy of labour induction compared with expectant management is associated with fewer deaths of babies and probably fewer caesarean sections; with probably little or no difference in assisted vaginal births. The best timing of when to offer induction of labour to women at or beyond 37 weeks' gestation warrants further investigation, as does further exploration of risk profiles of women and their values and preferences. Discussing the risks of labour induction, including benefits and harms, may help women make an informed choice between induction of labour for pregnancies, particularly those continuing beyond 41 weeks, or waiting for labour to start and/or waiting before inducing labour. Women's understanding of induction, the procedures, their risks and benefits, is important in influencing their choices and satisfaction.

Summary of findings

Summary of findings 1. Labour induction versus expectant management (infant/child outcomes).

Induction of labour for improving birth outcomes for women at or beyond 37 weeks gestation
Population: pregnant women at or beyond 37 weeks gestation Setting: Austria, Canada, China, India, Finland, Malaysia, Netherlands, Norway, Russia, Spain, Sweden, Thailand, Tunisia, Turkey, UK and USA Intervention: labour induction Comparison: expectant management
Outcomes	*Anticipated absolute effects^ (95% CI)**		Relative effect (95% CI)	№ of participants (studies)	Quality of the evidence (GRADE)	Comments
	Risk with expectant management	Risk with labour induction
Perinatal death (intrauterine deaths plus neonatal deaths in the first week of life)	Study population		RR 0.31 (0.15 to 0.64)	18,795 (22 RCTs)	⊕⊕⊕⊕ HIGH¹	Exact day of death not reported for all of the nine neonatal deaths but all were likely to have occurred in the first week of life (see Table 2)
	3 per 1000	0.4 per 1000 (0.1 to 1.9)
Stillbirth	Study population		RR 0.30 (0.12 to 0.75)	18,795 (22 RCTs)	⊕⊕⊕⊕ HIGH¹
	2 per 1000	1 per 1000 (0.15 to 1.5)
Admission to neonatal intensive care unit	Study population		RR 0.88 (0.80 to 0.96)	17,826 (17 RCTs)	⊕⊕⊕⊕ HIGH¹
	95 per 1000	83 per 1000 (80 to 91)
Neonatal encephalopathy	Study population		RR 0.69 (0.37 to 1.31)	8,851 (2 RCTs)	⊕⊕⊝⊝ LOW ²
	5 per 1000	3 per 1000 (2 to 7)
Apgar score less than 7 at 5 minutes	Study population		RR 0.73 (0.56 to 0.96)	18,345 (20 RCTs)	⊕⊕⊕⊝ MODERATE³
	13 per 1000	10 per 1000 (7 to 12)
Neonatal (birth) trauma	Study population		RR 0.97 (0.63 to 1.49)	13,106 (5 RCTs)	⊕⊕⊕⊝ MODERATE⁴
	7 per 1000	7 per 1000 (5 to 12)
Neurodevelopment at childhood follow‐up	Study population		‐	(0 RCTs)	‐	No RCTs reported data for this outcome.
	see comment	see comment
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; RCT: randomised controlled trial; RR: risk ratio
GRADE Working Group grades of evidence High quality: we are very confident that the true effect lies close to that of the estimate of the effect Moderate quality: we are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low quality: our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low quality: we have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

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¹Not downgraded (larger studies (> 1000 participants) are generally at low risk of bias, although some smaller studies have unclear risk of selection bias); not downgraded for lack of blinding as unlikely to have influenced objective outcomes.

²Downgraded 2 levels for very serious concerns regarding imprecision (wide confidence intervals crossing the line of no effect).

³Downgraded 1 level for serious concerns regarding indirectness, with three studies reporting Apgar scores with more stringent cutoffs than < 5 at 7 minutes (see graph footnotes).

⁴Downgraded 1 level for serious concerns regarding imprecision, with wide confidence intervals crossing line of no effect.

5. Causes of death (stillbirths and livebirth deaths).

Study	Cause of death
Study	Intervention Group	Control Group (Expectant management)
Augensen 1987	No deaths	No deaths
Bergsjo 1989	1. Severe malformations (Livebirth) GA at birth and timing of death after birth not reported, but assumed to be early	1. Malformation (Livebirth) GA at birth and timing of death after birth not reported, but assumed to be early 2. Pneumonia (Livebirth) GA at birth and timing of death after birth not reported, but assumed to be early
Chanrachkul 2003	No deaths	No deaths
Cole 1975	No deaths	1. Congenital heart condition (Stillbirth) GA at detection of death not reported
Dyson 1987	No deaths	1. Meconium aspiration and persistent fetal circulation (Livebirth) GA at birth was 43 + 4 and timing of death after birth was early but not reported in days
Egarter 1989	No deaths	1. Cord complication (Stillbirth) GA at detection of fetal death was 40 + 3 weeks
Gelisen 2005	No deaths	1. Intrauterine fetal death (Stillbirth) GA at death 41 + 5 weeks
Grobman 2018	Antepartum stillbirth: 1 Intrapartum stillbirth: 0 Neonatal death: 1	Antepartum stillbirth: 1 Intrapartum stillbirth: 0 Neonatal death: 2 early deaths (no other information; time of death not reported)
Hannah 1992	No deaths	1. Hypoxic ischaemic encephalopathy (Stillbirth) GA at detection of death not reported in days 2. Massive aspiration of meconium (Stillbirth) GA at detection of death not reported
Heimstad 2007	No deaths	1. Birth asphyxia secondary to a true knot in the umbilical cord (Livebirth) Birth at 294 days GA; death at 2 days of age
Henry 1969	No deaths	1. Stillbirth in a woman with an abnormal glucose tolerance test (Stillbirth) GA at detection of death not reported 2. Neonatal death from meconium inhalation in a woman with a positive amnioscopy who refused surgical induction of labour (Livebirth) GA at detection of death not reported, but presumed early
Herabutya 1992	No deaths	1. Congenital anomaly (Livebirth) Birth at 43 weeks; death at 3 days of age
James 2001	No deaths	No deaths
Keulen 2019	One fetal death: “The stillbirth in the induction group was in a 30 year old multiparous woman who was randomised at 40 weeks+5 days and scheduled for induction at 41 weeks+1 day. She had reduced fetal movements at 40 weeks+6 days, and fetal death was diagnosed at consultation. She delivered a neonate weighing 3595 g (20th to 50th centiles). Investigations, including a postmortem examination, did not explain the stillbirth.”	2 fetal deaths: "stillbirth was diagnosed in a 36 year old nulliparous woman at 41 weeks+3 days, when she was admitted to hospital in labour. She delivered a neonate weighing 2945 g (5th to 10th centiles). Investigations, including placental examination, did not explain the stillbirth, and the parents declined a postmortem examination. The second stillbirth in the expectant management group was diagnosed in a 32 year old multiparous woman at 41 weeks+4 days during a regular consultation in secondary care for impending post‐term pregnancy. She delivered a neonate weighing 3715 g (20th to 50th centiles). No postmortem examination was performed, but the placenta showed signs of chorioamnionitis.”
Martin 1978	No deaths reported	1 (Stillbirth) Stillbirth after induction of labour at 42 weeks for postmaturity and meconium
Martin 1989	No deaths	No deaths
NICHHD 1994	No deaths	No deaths
Sargunam 2019	No deaths reported	No deaths reported
Sahraoui 2005	No deaths	1 (Intrauterine fetal death) (Stillbirth) Death detected at 42 weeks' GA
Sande 1983	No deaths	No deaths
Suikkari 1983	No deaths	No deaths
Walker 2016	No deaths	No deaths
Wennerholm 2019	No deaths	6 (5 stillbirths; 1 early neonatal death) One stillborn baby had cardiovascular malformations not considered to be lethal and there were no explanations for the deaths of the other four stillbirths; Cause of the early neonatal death was hypoxic ischaemic encephalopathy in a large for gestational age neonate.

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^GA:^{gestational age}

Summary of findings 2. Labour induction versus expectant management (maternal outcomes).

Induction of labour for improving birth outcomes for women at or beyond term
Population: pregnant women at or beyond 37 weeks gestation Setting: Austria, Canada, China, Finland, France, India, Malaysia, Netherlands, Norway, Spain, Sweden, Russia, Thailand, Tunisia, Turkey, UK, and USA Intervention: labour induction Comparison: expectant management
Outcomes	*Anticipated absolute effects^ (95% CI)**		Relative effect (95% CI)	№ of participants (studies)	Quality of the evidence (GRADE)	Comments
	Risk with expectant management	Risk with labour induction
Caesarean section	Study population		RR 0.90 (0.85 to 0.95)	21,030 (31 RCTs)	⊕⊕⊕⊝ MODERATE¹
	186 per 1000	167 per 1000 (158 to 177)
Operative vaginal birth (forceps or ventouse)	Study population		RR 1.03 (0.96 to 1.10)	18,584 (22 RCTs)	⊕⊕⊕⊝ MODERATE¹
	136 per 1000	140 per 1000 (131 to 150)
Perineal trauma (severe perineal tear)	Study population		RR 1.04 (0.85 to 1.26)	11,589 (5 RCTs)	⊕⊕⊝⊝ LOW^1,2
	31 per 1000	33 per 1000 (26 to 39)
Postpartum haemorrhage	Study population		RR 1.02 (0.91 to 1.15)	12,609 (9 RCTs)	⊕⊕⊕⊝ MODERATE³	variously defined
	79 per 1000	81 per 1000 (73 to 91)
Breastfeeding at discharge	Study population		RR 1.00 (0.96 to 1.04)	7487 (2 RCTs)	⊕⊕⊕⊝ MODERATE⁴
	505 per 1000	505 per 1000 (485 to 525)
Postnatal depression	Study population		‐	(0 RCTs)	‐	No RCTs reported data for this outcome.
	see comment	see comment
Length of maternal hospital stay (days)	‐	‐	Average MD 0.19 days shorter for women who were induced (0.56 days shorter to 0.18 days longer)	4120 (7 RCTs)	⊕⊝⊝⊝ VERY LOW⁵
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; MD: mean difference; RCT: randomised controlled trial; RR: risk ratio
GRADE Working Group grades of evidence High quality: we are very confident that the true effect lies close to that of the estimate of the effect Moderate quality: we are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low quality: our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low quality: we have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

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¹Downgraded 1 level for serious concerns regarding unclear allocation concealment methods for many of the 31 trials included for this outcome. ²Downgraded 1 level for serious concerns regarding imprecision with wde confidence intervals crossing the line of no effect, signalling some uncertainty about direction of effect.

³Downgraded 1 level for serious concerns regarding indirectness with postpartum haemorrhage defined in different ways for several of the trials.

⁴Downgraded 1 level for indirectness with one of the two studies reporting breastfeeding 4‐8 weeks after discharge (not at discharge).

⁵Downgraded 1 level for serious concerns regarding selection bias, with 4 of 5 trials having with unclear allocation concealment; and downgraded 2 levels for very serious concerns regarding inconsistency, with very high statistical heterogeneity (I² = 94%).

Background

Description of the condition

Pregnancies continuing beyond 294 days (42⁰ weeks) are described as being 'post‐term' or 'postdate' (Roos 2010). In 2017 in the USA, 5.8% of pregnancies progressed to 41+ weeks (Martin 2018), dropping from around 10% a decade or so earlier (Olesen 2003; Zeitlin 2007). However the definition of term pregnancy is less clear, with increasing calls for term to be redefined as close to 40 completed weeks as possible (University of Sydney 2020).

While the aetiology of post‐term birth is not well elucidated (Mandruzzato 2010), risk factors such as obesity, nulliparity and maternal age greater than 30 years have been associated with an increased risk of post‐term birth (Arrowsmith 2011; Caughey 2009; Heslehurst 2017; Roos 2010). Placental senescence may play a role in the pathophysiology of post‐term birth (Mandruzzato 2010), and genetic/epigenetic factors have also been implicated (Schierding 2014).

In a systematic review of 15 million pregnancies from high‐income countries, the risk of stillbirth increased with gestational age, from 0.11 per 1000 births at 37 weeks' gestation to 3.18 per 1000 births at 42 weeks' gestation; and risk of neonatal death was nearly doubled for pregnancies continuing beyond 41 weeks, compared with 38‐41 weeks' gestation (Muglu 2019). In a large retrospective cohort study from the United States, involving 5.4 million pregnancies of low‐risk, parous women at 39 to 41 weeks' gestation, overall risks of a composite adverse neonatal outcome (any of: Apgar score less than five at five minutes, assisted ventilation for longer than six hours, neonatal seizure or neonatal mortality) and a composite adverse maternal outcome (any of: intensive care unit admission, blood transfusion, uterine rupture, or unplanned hysterectomy) increased from 39 through to 41 weeks (Chen 2019). These findings are important in that, even in settings where early booking allows accurate assessment of gestational age and antenatal services are accessible for most women, post‐term pregnancy still constitutes a high‐risk situation, especially for the baby.

The obstetric problems associated with post‐term pregnancy include induction of labour with an unfavourable cervix, caesarean section, prolonged labour, postpartum haemorrhage and traumatic birth. It is likely that some of these unwanted outcomes result from intervening when the uterus and cervix are not ready for labour (Caughey 2004).

Description of the intervention

Induction of labour is widely practised to try and prevent outcomes such as caesarean section, prolonged labour, postpartum haemorrhage and traumatic birth (Caughey 2004), and to improve health outcomes for women and their infants. Rates of induction of labour have increased over recent decades, with between and within country variations (Coates 2020; Marconi 2019). In the USA in 2017, one in four births (25.7%) was induced (Martin 2018). In Australia, the induction rate rose from 25% in 2007 to 33% in 2017 (AIHW 2019). For post‐term pregnancies, one in every two births may be induced (e.g. 52% induction rate for gestations ≥ 41 weeks as reported by Wolff 2016).

Variation in rates of post‐term births suggests that different policies and practices for managing post‐term pregnancies (especially timing of inductions) are used in Europe (Zeitlin 2007), and elsewhere. There is concern about increasing caesarean rates, despite induction rates also rising (Keirse 2010).

Earlier versions of this review included interventions involving monitoring, such as early pregnancy ultrasound, that may have an effect on the outcomes of pregnancies for women at or beyond 37 weeks. This topic is addressed in the Cochrane Review 'Ultrasound for fetal assessment in early pregnancy' (Whitworth 2015). In this update, we evaluated the effects of timing of labour induction at or beyond 37 weeks compared with expectant management (which may include various intensities and forms of monitoring).

How the intervention might work

Methods of induction of labour aim to induce cervical ripening and/or the onset of uterine contractions, and primarily include pharmacological methods (such as prostaglandins and oxytocin) and mechanical methods (such as the Foley catheter, double balloon catheter and artificial rupture of amniotic membranes: 'amniotomy'). Prostaglandins (misoprostol: prostaglandin E1 ‐ with oral, buccal/sublingual or vaginal administration; and dinoprostone: prostaglandin E2 ‐ available as vaginal gels or pessaries) are commonly used when the cervix is not favourable. When the cervix is favourable, oxytocin is usually used. The Foley catheter and/or amniotomy may be used alone, or in association with oxytocin, or misoprostol (Marconi 2019).

Why it is important to do this review

Determining the threshold for induction of post‐term pregnancies has been described as 'the 41 week to 42 week dilemma' (Keulen 2018), with many clinical practice guidelines now recommending a policy of induction at 41 weeks rather than a policy of waiting to induce at 42 weeks if spontaneous labour has not occurred (ACOG 2014; New Zealand Guideline Development Panel 2019; NICE 2008; SOGC 2017; WHO 2018). As there are no agreed standards for the timing of induction of labour, with guidance varying considerably internationally and nationally, debate continues (Coates 2020). Much uncertainty surrounds the optimal timing for induction, with clinical practice, and research studies in some settings, demonstrating trends towards earlier gestations at induction (Coates 2020).

It is important to assess whether improved outcomes such as reduced perinatal death and fewer caesarean sections can be achieved without negative impacts of being born too early, by choosing a window of timing for induction, and to determine optimal gestational thresholds, which may differ according to individual characteristics of women (Alavifard 2019).

Objectives

Methods

Criteria for considering studies for this review

Types of studies

We included randomised controlled trials. We included trials presented only as abstracts as well as trials published in full‐text manuscript format.

Cluster‐randomised trials, quasi‐randomised trials and cross‐over trials were not eligible for inclusion in this review.

Types of participants

We included pregnant women at or beyond 37 weeks. Since a risk factor at this stage of pregnancy would normally require an intervention, only trials including women at low risk for complications were eligible. We accepted the trialists' definition of 'low risk'. The trials of induction of labour exclusively in women with prelabour rupture of membranes at or beyond term were not considered in this review (and are considered in the Cochrane Review 'Planned early birth versus expectant management (waiting) for prelabour rupture of membranes at term (37 weeks or more)' (Middleton 2017), although some women participating in the eligible trials in this review may have had ruptured membranes.

Types of interventions

The intervention evaluated in this review is a policy of labour induction at a predetermined gestational age at or beyond 37 weeks. This policy is compared with 'expectant management' until an indication for birth arises. The trial protocols differ according to:

gestational age used in the induction of labour policy;
actual method of labour induction (prostaglandins, misoprostol, +/‐ oxytocin);
protocol used (dosage of any drugs, timing, frequency of use and mode of administration);
expectant management protocols (intensity of fetal well‐being assessment and fetal monitoring techniques used).

Types of outcome measures

Primary outcomes

Perinatal death (defined as intrauterine death plus neonatal death in the first week of life)

Secondary outcomes

For the infant/child

Stillbirth
Neonatal death within first week
Birth asphyxia (as defined by trialists)
Admission to neonatal intensive care unit
Neonatal convulsions
Neonatal encephalopathy
Use of anticonvulsants
Meconium aspiration syndrome
Pneumonia
Apgar score less than seven at five minutes
Birthweight
Birthweight > 4000 g
Neonatal trauma
Neurodevelopment at childhood follow‐up

For the mother

Mode of birth (caesarean section)
Operative vaginal birth (forceps or ventouse)
Analgesia used
Perineal trauma
Prolonged labour (cut‐off used by the trialists was used)
Postpartum haemorrhage (cut‐off used by the trialists was used)
Anxiety before birth
Other measures of satisfaction with the approach
Breastfeeding at discharge
Postnatal depression

Health services use

Length of maternal postnatal stay
Length of neonatal postnatal stay
Length of labour

Cost‐related analyses are described in the Discussion.

Search methods for identification of studies

The following methods section of this review is based on a standard template used by Cochrane Pregnancy and Childbirth.

Electronic searches

We searched Cochrane Pregnancy and Childbirth’s Trials Register by contacting their Information Specialist (17 July 2019).

The Register is a database containing over 25,000 reports of controlled trials in the field of pregnancy and childbirth. It represents over 30 years of searching. For full current search methods used to populate Pregnancy and Childbirth’s Trials Register including the detailed search strategies for CENTRAL, MEDLINE, Embase and CINAHL, the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service, please follow this link.

Briefly, Cochrane Pregnancy and Childbirth’s Trials Register is maintained by the Information Specialist and contains trials identified from:

monthly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);
weekly searches of MEDLINE (Ovid);
weekly searches of Embase (Ovid);
monthly searches of CINAHL (EBSCO);
handsearches of 30 journals and the proceedings of major conferences;
weekly current awareness alerts for a further 44 journals plus monthly BioMed Central email alerts.

Search results are screened by two people and the full text of all relevant trial reports identified through the searching activities described above is reviewed. Based on the intervention described, each trial report is assigned a number that corresponds to a specific Pregnancy and Childbirth review topic (or topics), and is then added to the Register. The Information Specialist searches the Register for each review using this topic number rather than keywords. This results in a more specific search set that has been fully accounted for in the relevant review sections (Included studies; Excluded studies; Studies awaiting classification; Ongoing studies).

In addition, we searched ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) for unpublished, planned and ongoing trial reports (17 July 2019) (see: Appendix 1 for search methods used).

Searching other resources

We searched the reference lists of retrieved studies. We did not apply any language or date restrictions.

Data collection and analysis

For methods used in the previous versions of this review, seeGülmezoglu 2012; and Middleton 2018.

For this update, the following methods were used for assessing the reports that were identified as a result of the updated search. Where required, information pertaining to the previously included studies was updated according to methods outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).

Selection of studies

Two review authors independently assessed for inclusion all the potential studies identified as a result of the search strategy. We resolved any disagreement through discussion or, if required, we consulted the third review author.

Data extraction and management

We designed a form to extract data. For eligible studies, two review authors extracted the data using the agreed form. We resolved discrepancies through discussion or, if required, we consulted the third review author. Data were entered into Review Manager software (RevMan 2014), and checked for accuracy.

When information regarding any of the above was unclear, we planned to contact authors of the original reports to provide further details.

Assessment of risk of bias in included studies

Two review authors independently assessed risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Any disagreement was resolved by discussion or by involving the third review author.

(1) Allocation (checking for possible selection bias)

We described for each included study the method used to generate the allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups.

We assessed the method as:

low risk of bias (any truly random process, e.g. random number table; computer random number generator);
high risk of bias (any non‐random process, e.g. odd or even date of birth; hospital or clinic record number);
unclear risk of bias.

(2) Allocation concealment (checking for possible selection bias)

We described for each included study the method used to conceal allocation to interventions prior to assignment and assessed whether the intervention allocation could have been foreseen in advance of, or during recruitment, or changed after assignment.

We assessed the methods as:

low risk of bias (e.g. telephone or central randomisation; consecutively numbered sealed opaque envelopes);
high risk of bias (open random allocation; unsealed or non‐opaque envelopes, alternation; date of birth);
unclear risk of bias.

(3.1) Blinding of participants and personnel (checking for possible performance bias)

We described for each included study the methods used, if any, to blind study participants and personnel from knowledge of which intervention a participant received. We considered that studies were at low risk of bias if they were blinded, or if we judged that the lack of blinding was unlikely to affect results. We assessed blinding separately for different outcomes or classes of outcomes.

We assessed the methods as:

low, high or unclear risk of bias for participants;
low, high or unclear risk of bias for personnel.

(3.2) Blinding of outcome assessment (checking for possible detection bias)

We described for each included study the methods used, if any, to blind outcome assessors from knowledge of which intervention a participant received. We assessed blinding separately for different outcomes or classes of outcomes.

We assessed methods used to blinded outcome assessment as:

low, high or unclear risk of bias.

(4) Incomplete outcome data (checking for possible attrition bias due to the amount, nature and handling of incomplete outcome data)

We described for each included study, and for each outcome or class of outcomes, the completeness of data including attrition and exclusions from the analysis. We stated whether attrition and exclusions were reported and the numbers included in the analysis at each stage (compared with the total randomised participants), reasons for attrition or exclusion where reported, and whether missing data were balanced across groups or were related to outcomes. Where sufficient information was reported, or could be supplied by the trial authors, we planned to re‐include missing data in the analyses which we undertook.

We assessed methods as:

low risk of bias (e.g. no missing outcome data; missing outcome data balanced across groups);
high risk of bias (e.g. numbers or reasons for missing data imbalanced across groups; ‘as treated’ analysis done with substantial departure of intervention received from that assigned at randomisation);
unclear risk of bias.

(5) Selective reporting (checking for reporting bias)

We described for each included study how we investigated the possibility of selective outcome reporting bias and what we found.

We assessed the methods as:

low risk of bias (where it is clear that all of the study’s prespecified outcomes and all expected outcomes of interest to the review have been reported);
high risk of bias (where not all the study’s prespecified outcomes have been reported; one or more reported primary outcomes were not prespecified; outcomes of interest are reported incompletely and so cannot be used; study fails to include results of a key outcome that would have been expected to have been reported);
unclear risk of bias.

(6) Other bias (checking for bias due to problems not covered by (1) to (5) above)

We described for each included study any important concerns we had about other possible sources of bias.

(7) Overall risk of bias

We made explicit judgements about whether studies were at high risk of bias, according to the criteria given in the Handbook (Higgins 2011). With reference to (1) to (6) above, we assessed the likely magnitude and direction of the bias and whether we considered it was likely to have impacted on the findings. We explored the impact of the level of bias through undertaking sensitivity analyses ‐ seeSensitivity analysis.

Measures of treatment effect

Dichotomous data

For dichotomous data, we presented results as summary risk ratio with 95% confidence intervals.

Continuous data

For continuous data, we used the mean difference. We planned to use the standardised mean difference to combine trials that measured the same outcome, but used different methods.

Unit of analysis issues

Cluster‐randomised trials

Cluster‐randomised trials were not eligible for inclusion.

Cross‐over trials

Cross‐over trials were not eligible for inclusion.

Multiple pregnancies

We did not identify any eligible studies that reported multiple pregnancies separately. If studies with multiple pregnancies are reported separately in trials included in future updates of this review, we will adjust for clustering in the analyses wherever possible, and use the inverse variance method for adjusted analyses, as described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011), and in Yelland 2011.

Multi‐armed trials

Where we included studies with multiple arms, we created single pairwise comparisons, by including only the groups relevant to this review, or by combining groups. In Gelisen 2005, we combined the three induction arms for the relevant analyses.

Dealing with missing data

For included studies, we noted levels of attrition. In future updates, if more eligible studies are included, we will explore the impact of including studies with high levels of missing data in the overall assessment of treatment effect by using sensitivity analyses.

For all outcomes, we carried out analyses, as far as possible, on an intention‐to‐treat basis, i.e. we attempted to include all participants randomised to each group in the analyses. The denominator for each outcome in each trial was the number randomised minus any participants whose outcomes were known to be missing.

Assessment of heterogeneity

We assessed statistical heterogeneity in each meta‐analysis using the Tau², I² and Chi² statistics. We regarded heterogeneity as substantial if an I² was greater than 30% and either the Tau² was greater than zero, or there was a low P value (less than 0.10) in the Chi² test for heterogeneity. Where we identified substantial heterogeneity (above 30%), we aimed to explore it using prespecified subgroup analyses.

Assessment of reporting biases

Where there were 10 or more studies in the meta‐analyses, we investigated reporting biases (such as publication bias) using funnel plots. We assessed funnel plot asymmetry visually. If asymmetry was suggested by a visual assessment, we planned to perform exploratory analyses to investigate it.

Data synthesis

We carried out statistical analysis using the Review Manager software (RevMan 2014). We used fixed‐effect meta‐analysis for combining data where it was reasonable to assume that studies were estimating the same underlying treatment effect: i.e. where studies were examining the same intervention, and the studies' populations and methods were judged sufficiently similar. The denominators used for neonatal outcomes were the whole randomised population (without the stillbirths removed).

Where there was clinical heterogeneity sufficient to expect that the underlying treatment effects differed between trials, or where substantial statistical heterogeneity was detected, we used random‐effects meta‐analysis to produce an overall summary if an average treatment effect across trials was considered clinically meaningful. The random‐effects summary has been treated as the average of the range of possible treatment effects and we have discussed the clinical implications of treatment effects differing between trials. If the average treatment effect was not clinically meaningful, we decided that we would not combine trials. Where we used random‐effects analyses, the results have been presented as the average treatment effect with 95% confidence intervals, and the estimates of Tau² and I².

Subgroup analysis and investigation of heterogeneity

Where we identified substantial heterogeneity, we planned to investigate it using subgroup and sensitivity analyses. We planned to consider whether an overall summary was meaningful, and if it was, we used random‐effects analysis to produce it.

We carried out the following subgroup analyses.

Gestational age by week of gestation when induction was intended in the intervention arm
- in this update, we have presented the main groups as gestational ages < 40 weeks, 40‐41 weeks, and > 41 completed weeks (> 287 days).
Parity (nulliparous versus mixed parity (primi‐ and multiparous versus not stated).
State of the cervix (favourable versus unfavourable versus unknown or mixed status).

We were unable to conduct subgroup analyses by method of induction, due to wide variation in reporting of dosage, timing, frequency and mode of administration.

Where possible, we used the following outcomes in subgroup analyses.

For the infant/child

Perinatal death, defined as intrauterine deaths plus neonatal deaths in the first week of life
Stillbirth
Admission to neonatal intensive care unit

For the mother

Mode of birth (caesarean section)
Operative vaginal birth (forceps or ventouse)
Perineal trauma

We assessed subgroup differences by interaction tests available within RevMan (RevMan 2014). We reported the results of subgroup analyses quoting the Chi² statistic and P value, and the interaction test I² value.

Sensitivity analysis

We carried out sensitivity analyses to explore the effect of trial risk of bias assessed by concealment of allocation, high attrition rates, or both, with studies at high risk of bias being excluded from the analyses in order to assess whether this made any difference to the overall result. We used the following outcomes in our sensitivity analyses. If enough data becomes available in future updates, we will explore the impact of including studies with high levels of missing data in the overall assessment of treatment effect by using sensitivity analyses.

For the infant/child

Perinatal death, defined as intrauterine deaths plus neonatal deaths in the first week of life
Stillbirth
Admission to neonatal intensive care unit

For the mother

Mode of birth (caesarean section)
Operative vaginal birth (forceps or ventouse)
Perineal trauma

Assessment of the certainty of the evidence using the GRADE approach

For this update, we used the GRADE approach as outlined in the GRADE handbook, in order to assess the certainty of the body of evidence relating to the following outcomes.

For the infant/child

Perinatal death, defined as intrauterine deaths plus neonatal deaths in the first week of life
Stillbirth
Admission to neonatal intensive care unit
Neonatal encephalopathy
Apgar score less than seven at five minutes
Neonatal trauma
Neurodevelopment at childhood follow‐up

For the mother

Mode of birth (caesarean section)
Operative vaginal birth (forceps or ventouse)
Perineal trauma (e.g. severe perineal tear)
Postpartum haemorrhage (cut‐off reported by the trialists was used)
Breastfeeding at discharge
Postnatal depression
Length of maternal postnatal stay

We used the GRADEpro Guideline Development Tool to import data from Review Manager 5.3 (RevMan 2014), in order to create ’Summary of findings’ tables, comparing a policy of labour induction versus expectant management. A summary of the intervention effect and a measure of certainty for each of the above outcomes was produced using the GRADE approach. The GRADE approach uses five considerations (study limitations, consistency of effect, imprecision, indirectness and publication bias) to assess the certainty of the body of evidence for each outcome. The evidence can be downgraded from 'high certainty' by one level for serious (or by two levels for very serious) limitations, depending on assessments for risk of bias, indirectness of evidence, serious inconsistency, imprecision of effect estimates or potential publication bias.

Results

Description of studies

Results of the search

See Figure 1.

For this update, we assessed 14 new trial reports, and re‐assessed three ongoing studies, Wennerholm 2019 (classified as Elden 2016 in the previous version of this review); Grobman 2018 (classified as NCT01990612 in the previous version of this review); ISRCTN15646866; and re‐assessed two studies which were previously awaiting further classification (Benito Reyes 2010; ISRCTN74323479)).

We included four new studies (11 reports) (Baev 2017; Grobman 2018; Sargunam 2019; Wennerholm 2019), excluded two new studies (two reports) (PACTR201805002872322; CTRI/2018/09/015719), and listed one new study as ongoing (one report) (ISRCTN83219789). Three of the new reports related to an already included study (Keulen 2019 (Kortekaas 2014 in the previous version of this review)). Two of the previously ongoing studies related to trial protocols for two newly included studies (Grobman 2018; Wennerholm 2019); and one of the previously ongoing studies (ISRCTN15646866) remains ongoing. Benito Reyes 2010 and ISRCTN74323479 remain awaiting classification (requiring an English translation, and further details, to assess eligibility respectively).

Therefore, 34 studies are included in this update (69 reports), two studies are ongoing (two reports), 66 studies are excluded (77 reports), and two studies (two reports) await further classification.

Included studies

Settings

Of the 34 included trials:

seven were conducted in the USA (Dyson 1987; Grobman 2018; Martin 1989; Miller 2015; NICHHD 1994; Nielsen 2005; Witter 1987);
four in the UK (Scotland; England; Ireland) (Cole 1975; Henry 1969; Martin 1978; Walker 2016);
three in China (Bergsjo 1989; Cohn 1992; Roach 1997);
three in Norway (Augensen 1987; Heimstad 2007; Sande 1983);
three in Sweden (Brane 2014; Tylleskar 1979; Wennerholm 2019);
two in India (Chakravarti 2000; James 2001);
two in Thailand (Chanrachkul 2003; Herabutya 1992);
one in Tunisia (Sahraoui 2005);
one in Turkey (Gelisen 2005);
one in Canada (Hannah 1992);
one in France (Breart 1982);
one in Austria (Egarter 1989);
one in Spain (Ocon 1997);
one in the Netherlands (Keulen 2019);
one in Malaysia (Sargunam 2019);
one in Finland (Suikkari 1983); and
one in Russia (Baev 2017).

Date trials published/conducted

Four trials were published in or before the 1970s (Cole 1975; Henry 1969; Martin 1978; Tylleskar 1979)
Nine trials were published in the 1980s (Augensen 1987; Bergsjo 1989; Breart 1982; Dyson 1987; Egarter 1989; Martin 1989; Sande 1983; Suikkari 1983; Witter 1987)
Six trials were published in the 1990s (Cohn 1992; Hannah 1992; Herabutya 1992; NICHHD 1994; Ocon 1997; Roach 1997)
Seven trials were published in the 2000s (Chakravarti 2000; Chanrachkul 2003; Gelisen 2005; Heimstad 2007; James 2001; Nielsen 2005; Sahraoui 2005)
Eight trials were published in the 2010s (Baev 2017; Brane 2014; Grobman 2018; Keulen 2019; Miller 2015; Sargunam 2019; Walker 2016; Wennerholm 2019).

Over half the total participants (12,074) were recruited from trials published in the last seven years.

Cervix status

Ten trials did not mention cervix status as an inclusion criterion (Bergsjo 1989; Breart 1982; Chakravarti 2000; Cohn 1992; Cole 1975; Henry 1969; James 2001; Roach 1997; Suikkari 1983; Witter 1987). Ten trials included women with unfavourable cervix (Baev 2017; Dyson 1987; Gelisen 2005; Hannah 1992; Herabutya 1992; Martin 1989; Miller 2015; NICHHD 1994; Ocon 1997; Sahraoui 2005), and five with favourable cervical status (Chanrachkul 2003; Egarter 1989; Nielsen 2005; Sande 1983; Tylleskar 1979). Nine trials included women with mixed cervical status (Augensen 1987 (35% of women with unfavourable cervix); Brane 2014; Grobman 2018; Heimstad 2007; Keulen 2019; Martin 1978; Sargunam 2019; Walker 2016; Wennerholm 2019).

Interventions

All trials were conducted in hospitals with various intensities of fetal monitoring both in the induction and expectant management groups (seeCharacteristics of included studies).

Timing of induction ‐ induction group

The information on timing of induction in each trial is outlined in Table 4.

1. Gestational age, at baseline and at induction.

Study	At baseline/enrolment (all participants)	At induction (intervention group participants only) Mean [SD] unless otherwise indicated
Augensen 1987	41 weeks (290‐297 days)	294.8 days **(category: ≥ 41 weeks)**
Baev 2017	40⁺⁶ weeks (283‐289 days)	285.35 [0.93] days *(category: 40‐41 weeks)*
Bergsjo 1989	42 weeks⁺ (294⁺ days)	294⁺ days, mean NR **(category: ≥ 41 weeks)**
Brane 2014	between 37⁺⁰ and 41⁺⁶ weeks	282 [5.9] days *(category: 40‐41 weeks)*
Breart 1982	37 to 39 weeks (259‐273 days)	259‐273 days, mean NR *(category: < 40 weeks)*
Chakravarti 2000	< 41 weeks (< 290 days)	< 290 days, mean NR *(category: 40‐41 weeks)*
Chanrachkul 2003	41⁺³ weeks (290 days)	290.4 [1.4] days **(category: ≥ 41 weeks)**
Cohn 1992	42⁺⁰ weeks (294 days)	294⁺ days **(category: ≥ 41 weeks)**
Cole 1975	39 to 40 weeks (273‐280 days)	273‐280 days, mean NR *(category: < 40 weeks)*
Dyson 1987	41 weeks⁺ (287 days⁺)	296.3 [2.6] days **(category: ≥ 41 weeks)**
Egarter 1989	40 weeks (280 days)	280 days (category: 40 to 41 weeks )
Gelisen 2005	41 weeks^{+ 0‐1}	286‐288 days (category: ≥ 41 weeks)
Grobman 2018	38⁰ weeks to 38⁶ (268‐274 days)	39⁰ weeks to 39⁴ weeks (273‐279 days) *(category: < 40 weeks)*
Hannah 1992	41 weeks⁺ (287 days⁺)	287 days⁺ mean NR (authors stated that women were induced within 4 days of enrolment, and that 88% of women were 41 weeks GA, (287‐293 days GA), no further details) **(category: ≥ 41 weeks)**
Heimstad 2007	40⁶ weeks (286 days)	Mean 289 [0.7] days **(category: ≥ 41 weeks)**
Henry 1969	41 weeks⁺ (287 days⁺)	287⁺ days, mean NR **(category: ≥ 41 weeks)**
Herabutya 1992	42 weeks⁺ (294 days⁺)	294⁺ days, mean NR (category: ≥ 41 weeks)
James 2001	41 weeks (287 days)	287⁺ days, mean NR **(category: ≥ 41 weeks)**
Keulen 2019	40⁵ to 41⁰ weeks (285‐287 days)	287 to 288 days, mean NR **(category: ≥ 41 weeks)**
Martin 1978	37¹ to 37⁶ weeks (260‐266 days)	273 days *(category: < 40 weeks)*
Martin 1989	41 weeks (287 days)	287⁺ days, mean NR **(category: ≥ 41 weeks)**
Miller 2015	38⁰ to 38⁶ (266 to 272 days)	39⁰ to 39⁶ weeks (273‐279 days), mean NR *(category: < 40 weeks)*
NICHHD 1994	41 weeks⁺ (at least 287 days)	287 days to < 301 days, mean NR **(category: ≥ 41 weeks)**
Nielsen 2005	39⁰ to 39⁶ weeks (273‐279 days)	Within a week after enrolment, therefore between 39 and 40 weeks (274 to 280 days) (mean time between enrolment and induction of labour 3.7 days) *(category: < 40 weeks)*
Ocon 1997	Unclear (due to incomplete translation of paper)	42 completed weeks **(category: ≥ 41 weeks)**
Roach 1997	41⁰ to 41⁶ weeks (287 to 293 days)	42 completed weeks **(category: ≥ 41 weeks)**
Sahraoui 2005	41⁰ to 41⁶ weeks (287‐293 days)	287‐293 days, mean NR **(category: ≥ 41 weeks)**
Sande 1983	40⁰ and 40⁶ weeks	280 to 286 days *(category: 40 to 41 weeks)*
Sargunam 2019	≥ 39 weeks (≥ 273 days)	≥ 273 days *(category: < 40 weeks)*
Suikkari 1983	10 days or more post‐date	287⁺ days **(category: ≥ 41 weeks)**
Tylleskar 1979	At least 37 weeks (259⁺ days)	40 weeks, EDD +/‐ 2 days *(category: 40 to 41 weeks)*
Walker 2016	36⁰ to 39⁶ weeks (252‐279 days)	39⁰ to 39⁶ weeks (273‐279 days) *(category: < 40 weeks)*
Wennerholm 2019	40⁶ to 41¹ weeks (286 to 288 days)	288.7 [1.1] weeks **(category: ≥ 41 weeks)**
Witter 1987	41 weeks (293 to 298 days)	42 weeks (293‐298 days) **(category: ≥ 41 weeks)**

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^EDD^{: estimated due date GA: gestational age NR: not reported SD: standard deviation}

We have categorised timing of induction in the intervention arm into three groups:

induced at < 40 weeks: eight trials (Breart 1982; Cole 1975; Grobman 2018; Martin 1978; Miller 2015; Nielsen 2005; Sargunam 2019; Walker 2016);
induced between 40 to 41 weeks: six trials (Baev 2017; Brane 2014; Chakravarti 2000; Egarter 1989; Sande 1983; Tylleskar 1979);
induced at ≥ 41 weeks: 20 trials (Augensen 1987; Bergsjo 1989; Chanrachkul 2003; Cohn 1992; Dyson 1987; Gelisen 2005; Hannah 1992; Heimstad 2007; Henry 1969; Herabutya 1992; James 2001; Keulen 2019; Martin 1989; NICHHD 1994; Ocon 1997; Roach 1997; Sahraoui 2005; Suikkari 1983; Wennerholm 2019; Witter 1987).

Parity

Most of the 34 included trials included a mixture of primiparous and multiparous women:

primiparous women: six trials (Brane 2014; Chakravarti 2000; Grobman 2018; Miller 2015; Sargunam 2019; Walker 2016);
primiparous and multiparous women: 22 trials (Augensen 1987; Baev 2017; Bergsjo 1989; Breart 1982; Chanrachkul 2003; Cole 1975; Dyson 1987; Egarter 1989; Gelisen 2005; Hannah 1992; Heimstad 2007; Henry 1969; Herabutya 1992; Keulen 2019; Martin 1978; NICHHD 1994; Nielsen 2005; Sahraoui 2005; Sande 1983; Suikkari 1983; Tylleskar 1979; Wennerholm 2019);
not stated/unclear: six trials (Cohn 1992; James 2001; Martin 1989; Ocon 1997; Roach 1997; Witter 1987).

See Characteristics of included studies table and Table 5 for further details.

2. Parity.

Primiparous	Mixed (primi‐ and multiparous)	Not stated/not available
Brane 2014	Augensen 1987	Cohn 1992
Chakravarti 2000	Baev 2017	James 2001
Grobman 2018	Bergsjo 1989	Martin 1989
Miller 2015	Breart 1982	Ocon 1997
Sargunam 2019	Chanrachkul 2003	Roach 1997
Walker 2016	Cole 1975	Witter 1987
	Dyson 1987
	Egarter 1989
	Gelisen 2005
	Hannah 1992
	Heimstad 2007
	Henry 1969
	Herabutya 1992
	Keulen 2019
	Martin 1978
	NICHHD 1994
	Nielsen 2005
	Sahraoui 2005
	Sande 1983
	Suikkari 1983
	Tylleskar 1979
	Wennerholm 2019 (perinatal deaths reported by parity)

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Method of induction ‐ induction group

Labour induction was by oxytocin with or without artificial rupture of membranes in most trials. In trials recruiting women with an unfavourable cervix, priming with prostaglandins was often undertaken before induction.

Of the 34 included trials:

two trials did not report the method used (Chakravarti 2000; Cohn 1992);
27 trials used oxytocin infusion in some or all women in their intervention group (Augensen 1987; Baev 2017; Bergsjo 1989; Brane 2014; Breart 1982; Chanrachkul 2003; Cole 1975; Dyson 1987; Gelisen 2005; Grobman 2018; Hannah 1992; Heimstad 2007; Henry 1969; Herabutya 1992; James 2001; Keulen 2019; Martin 1989; Miller 2015; NICHHD 1994; Nielsen 2005; Sande 1983; Sargunam 2019; Suikkari 1983; Tylleskar 1979; Walker 2016; Wennerholm 2019; Witter 1987). Of those trials, only one used oxytocin as the sole method of induction (Augensen 1987). Twenty trials used artificial rupture of membranes (AROM) where indicated, as well as oxytocin infusion (when possible) (Baev 2017; Bergsjo 1989; Brane 2014; Breart 1982; Chanrachkul 2003; Cole 1975; Grobman 2018; Heimstad 2007; Henry 1969; Herabutya 1992; James 2001; Keulen 2019; Miller 2015; Nielsen 2005; Sande 1983; Sargunam 2019; Suikkari 1983; Tylleskar 1979; Walker 2016; Witter 1987);
none of the included trials used AROM as the sole method of induction;
13 trials used intravaginal prostaglandin E2 for some or all women in the intervention group (in either gel or pessary form) (Baev 2017; Brane 2014; Dyson 1987; Egarter 1989; Hannah 1992; Herabutya 1992; Keulen 2019; NICHHD 1994; Ocon 1997; Roach 1997; Sahraoui 2005; Walker 2016; Wennerholm 2019). Four trials used prostaglandin E2 as the sole method of induction (Egarter 1989; Ocon 1997; Roach 1997; Sahraoui 2005) and eight trials used a combination of prostaglandin and oxytocin +/‐ AROM (Baev 2017; Brane 2014; Dyson 1987; Hannah 1992; Herabutya 1992; Keulen 2019; NICHHD 1994; Walker 2016);
six trials used vaginal misoprostol in some or all women in the intervention group (Gelisen 2005; Heimstad 2007; Keulen 2019; Miller 2015; Sargunam 2019; Wennerholm 2019), and one used vaginal mifepristone in all women in the intervention group (Baev 2017);
in Keulen 2019, cervical priming was according to local protocol, which included prostaglandin E2, misoprostol, Foley catheter, double balloon catheter or a combination; and in Grobman 2018, the method of cervical priming (where indicated) was left to the discretion of the woman’s obstetric provider;
two trials had more than one intervention group (Gelisen 2005; NICHHD 1994), although the placebo priming and oxytocin arm in NICHHD 1994 was not included in this review. The Gelisen 2005 trial had three labour induction arms with misoprostol, oxytocin and Foley catheter.

Expectant management group protocols

For the majority of trials, expectant management protocols included various combinations of fetal heart rate monitoring, ultrasound for amniotic fluid measurements and, in earlier studies, biochemical tests.

No gestational age limit for induction in the expectant management groups was imposed or reported in 10 of the trials (Brane 2014; Cohn 1992; Dyson 1987; Henry 1969; James 2001; Ocon 1997; Roach 1997; Sargunam 2019; Suikkari 1983; Witter 1987). In the remaining 24 trials, women were induced at the following times (unless they went into spontaneous labour earlier) in the expectant management groups.

40⁵ to 42² weeks (Grobman 2018)
41 weeks (Cole 1975)
41 to 42 weeks (Walker 2016)
42 weeks (Baev 2017; Breart 1982; Chakravarti 2000; Egarter 1989; Gelisen 2005; Keulen 2019; Martin 1978; Miller 2015; Nielsen 2005; Sahraoui 2005; Sande 1983; Tylleskar 1979; Wennerholm 2019)
42 to 43 weeks (Augensen 1987; Heimstad 2007)
43 weeks (Bergsjo 1989; Martin 1989)
44 weeks (Chanrachkul 2003; Hannah 1992; Herabutya 1992; NICHHD 1994)

See Characteristics of included studies for further details.

Setting of induction is reported in Table 6.

3. Induction setting (start and waiting).

STUDY	START (hospital or home: and type of unit (obstetric or midwife‐led))	WAITING (hospital or home)
Augensen 1987	Hospital "Women in group 1 (immediate induction) were then referred to the delivery department for induction"	Not reported
Baev 2017	Hospital	Not reported
Bergsjo 1989	Hospital	Hospital (not explicitly stated that women in the induction group stayed in hospital after induction started). However authors reported that two women in the induction group (who waited up until a week for induction) stayed in hospital after randomisation, due to transport/distance issues). This suggests that some women waited at home.
Brane 2014	Hospital (Swedish delivery unit)	Hospital
Breart 1982	Unclear (in French)	Unclear (in French)
Chakravarti 2000	Not reported	Not reported
Chanrachkul 2003	Hospital	Hospital
Cohn 1992	Not reported	Not reported
Cole 1975	Hospital	Not reported
Dyson 1987	Hospital	Home and hospital: women who did not have a regular contractile pattern 45 minutes after induction gel was administered were allowed to go home; those who did were admitted to the hospital.
Egarter 1989	Not reported	Not reported
Gelisen 2005	Hospital	Hospital
Grobman 2018	Not reported (A specific induction protocol was not mandated for women who underwent induction in either group).	Not reported
Hannah 1992	Hospital (community and tertiary)	Not reported, only reported that when induction was started, women were treated as outpatients in the hospital
Heimstad 2007	Hospital	Not reported
Henry 1969	Hospital	Not reported
Herabutya 1992	Hospital	Home and hospital or either: women with a Bishop score > 6 stayed in hospital after the induction was performed, and sent to birthing ward; while those with a lower Bishop score were asked to go home and come in the next morning
James 2001	Hospital	Not reported
Keulen 2019	Primary care midwifery practices (n = 123) and hospitals (n = 45) (in the Netherlands, care is provided for women with normal risk pregnancies by midwives, and for pregnancies at increased risk by obstetricians or gynaecologists)	"all women in the 41 week induction group received obstetrician led intrapartum secondary care"
Martin 1978	Hospital	Hospital
Martin 1989	Hospital	Hospital
Miller 2015	Hospital	Hospital
NICHHD 1994	Hospital	Hospital
Nielsen 2005	Hospital	Not reported
Ocon 1997	Unclear (in Spanish)	Unclear (in Spanish)
Roach 1997	Hospital	Not reported
Sahraoui 2005	Not reported	Not reported
Sande 1983	Not reported	Not reported
Sargunam 2019	Hospital Not stated by authors, however implied by the trial inclusion criteria: "persistent contractions after overnight hospitalisation > 8 h"	Not reported
Suikkari 1983	Hospital	Not reported
Tylleskar 1979	"Two health clinics"	Health clinic where labour was induced
Walker 2016	Not reported: "In the induction group, local policies for induction of labor were followed".	Not reported
Wennerholm 2019	Not reported	Not reported
Witter 1987	Hospital	Not reported

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Outcomes

The primary outcome of perinatal death was reported in 22 of the 34 included trials. Caesarean section was reported in 31 trials. Operative vaginal birth (forceps or ventouse) was reported in 22 trials. Apgar score less than seven at five minutes, birthweight and admission to neonatal intensive care unit, were reported in 20, 18 and 17 trials, respectively. Other outcomes, such as many of the adverse pregnancy and neonatal outcomes, were reported in fewer than half of the included trials. Only three trials reported on maternal satisfaction and only two reported on breastfeeding. No trials reported on maternal anxiety or depression.

Funding

Twelve of the 34 included trials reported their funding sources as follows: Karolinska Institute Foundations and Funds (Brane 2014); Ramathibodi Hospital Research Grants (Chanrachkul 2003; Herabutya 1992); Community Service Program of Kaiser Foundation Hospitals (Dyson 1987); Eunice Kennedy Shriver National Institute of Child Health and Human Development (Grobman 2018); Medical Research Council of Canada (Hannah 1992); and Upjohn Company of Canada supplied the prostaglandin gel for this study; ZonMW: The Netherlands Organisation for Health Research and Development (Keulen 2019); Vicksburg Hospital Medical Foundation (Martin 1989); National Institute of Child Health and Human Development, NIH, USA (NICHHD 1994); University of Malaya (Sargunam 2019); other Research for Patient Benefit Programme of the National Institute for Health Research (Walker 2016); Swedish Government and county councils, Health Technology Centre at Sahlgrenska University Hospital, Foundation of the Health and Medical care committee of the Region of Vastra Gotaland, Sweden, Hjalmar Svensson Foundation, Foundation Mary von Sydow, born Wijk donation fund, Uppsala‐Orebro regional research council, region Orebro County research committee, ALF agreement in Stockholm, Centre for Clinical Research Dalama‐Uppsala University, Sweden (Wennerholm 2019).

One trial (Baev 2017) reported receiving no funding.

Twenty‐one of the 34 included trials did not report their funding sources.

Declarations of interest

Walker 2016 declared relevant interests on the part of one author, Dr Smith: "Dr. Smith reports receiving fees for serving on an advisory board from Roche Diagnostics, consulting fees from GlaxoSmithKline, equipment loans from Roche Diagnostics and General Electric, travel support from Roche Diagnostics and Chiesi, and grant support from GlaxoSmithKline and Action Medical Research, and being named as an inventor on a pending patent (PCT/EP2014/062602) filed by GlaxoSmithKline related to retosiban as a preventive treatment for preterm labour in women with increased uterine stretch". Grobman 2018 declared interests for one author: "Dr. Silver reports receiving consulting fees from Gestavision". The authors of these studies reported no other relevant potential conflict of interest. Keulen 2019 also declared interests from one author "BWM is supported by a National Health and Medical Research Council practitioner fellowship (GNT1082548) and reports consultancy for ObsEva, Merck, and Guerbet".

Baev 2017, Miller 2015 and Wennerholm 2019 declared no conflicts of interest.

None of the remaining 28 studies reported any declarations of interest.

Excluded studies

Most of the excluded trials were comparisons of different methods of labour induction (17 trials: Ascher‐Walsh 2000; De Aquino 2003; Evans 1983; Kipikasa 2005; Lee 1997; Lemancewicz 1999; Magann 1999; Mancuso 1998; Meydanli 2003; Misra 1994; Müller 1995; Papageorgiou 1992; Rijnders 2011; Satin 1991; Stenlund 1999; Su 1996; Surbek 1997) or cervical ripening protocols (28 trials: Bell 1993; Berghella 1996; Boulvain 1998; Buttino 1990; Damania 1992; Dare 2002; Doany 1997; Elliott 1984; El‐Torkey 1992; Giacalone 1998; Hage 1993; Ingemarsson 1987; Jenssen 1977; Kadar 1990; Klopper 1969; Lien 1998; Lyons 2001; Magann 1998; Newman 1997; Rayburn 1988; Rayburn 1999; Roberts 1986; Sawai 1991; Sawai 1994; Williams 1990; Wing 2000; Wong 2002; Ziaei 2003). Nine studies were not randomised trials (Amano 1999; Cardozo 1986; Garry 2000; Heden 1991; Hernandez‐Castro 2008; Iqbal 2004; Katz 1983; Knox 1979; Ohel 1996), in two trials pregnancies were not considered low risk (PACTR201805002872322; CTRI/2018/09/015719), and there were a variety of reasons for excluding the remaining 10 studies (Alcalay 1996; Conway 2000; Dunn 1989; Frass 2011; Gregson 2015; Imsuwan 1999; Neri 2014; Nicholson 2008; Paul 1988; Suzuki 1999). More details are provided in the Characteristics of excluded studies tables.

Risk of bias in included studies

Three trials (Chakravarti 2000; Cohn 1992; Suikkari 1983), were available only as abstracts and despite extensive searches we could not locate full publications of the studies, which limited our assessment of their risk of bias.

We judged the majority of included trials to be at low to moderate risk of bias (Figure 2; Figure 3), largely due to a lack of clear reporting.

'Risk of bias' graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

'Risk of bias' summary: review authors' judgements about each risk of bias item for each included study.

Allocation

We judged 18 trials (Augensen 1987; Baev 2017; Bergsjo 1989; Chanrachkul 2003; Dyson 1987; Grobman 2018; Heimstad 2007; James 2001; Keulen 2019; Martin 1978; Miller 2015; NICHHD 1994; Nielsen 2005; Sahraoui 2005; Sargunam 2019; Walker 2016; Wennerholm 2019; Witter 1987), to be at low risk of selection bias, reporting some form of adequate random sequencing such as a computer‐generated sequence or a list of random numbers. We judged the remaining 16 trials to be at unclear risk of selection bias, as they did not report how a random sequence was generated (Brane 2014; Breart 1982; Chakravarti 2000; Cohn 1992; Cole 1975; Egarter 1989; Gelisen 2005; Hannah 1992; Henry 1969; Herabutya 1992; Martin 1989; Ocon 1997; Roach 1997; Sande 1983; Suikkari 1983; Tylleskar 1979).

Of the 34 included trials, only 11 reported a method of allocation concealment likely to have a low risk of bias ‐ either central randomisation or sequentially numbered sealed opaque envelopes (Baev 2017; Grobman 2018; Hannah 1992; Heimstad 2007; Keulen 2019; Miller 2015; NICHHD 1994; Nielsen 2005; Sargunam 2019; Walker 2016; Wennerholm 2019). Eight trials reported that they used an envelope system with an unclear risk of bias (Brane 2014; Breart 1982; Dyson 1987; Gelisen 2005; James 2001; Martin 1989; Roach 1997; Witter 1987), one trial reported a partial third party system also with unclear risk of bias (Augensen 1987), and 14 trials did not report a method for concealing allocation and were rated as being at unclear risk of bias (Bergsjo 1989; Chakravarti 2000; Chanrachkul 2003; Cohn 1992; Cole 1975; Egarter 1989; Henry 1969; Herabutya 1992; Martin 1978; Ocon 1997; Sahraoui 2005; Sande 1983; Suikkari 1983; Tylleskar 1979).

Blinding

Performance bias

Given the nature of the intervention (induction of labour) and comparison (expectant management), it was not possible or not likely for women or clinicians to be blinded to the treatment group in any of the 34 trials, and thus risk of performance bias was judged to be high for 33 trials and unclear in Sargunam 2019. For the more objective outcomes such as perinatal death, this lack of blinding is unlikely to be a major source of bias.

Detection bias

It would have been possible for outcome assessment to have been undertaken by someone blinded to allocation groups, however, for the vast majority of studies (29), blinding, or lack of blinding, of outcome assessors was not explicitly stated. Keulen 2019 was assessed to be at low risk of detection bias, stating that "The statistician who performed the analyses was blinded to the allocation of the participants and performed the analysis according to a predefined analysis plan" and another trial (Martin 1978) reported blinded outcome assessment (also rated as low risk of bias). One study indicated partial blinding of outcome assessment (Hannah 1992), with an adjudication of abnormal neonatal outcomes undertaken by a neonatologist who was unaware of the mothers' group assignments (rated as unclear risk of bias). Grobman 2018 reported that assessment of neonatal primary outcomes "requiring review" were blinded, however, did not provide information regarding blinding of other outcome assessment (rated as unclear risk of bias). Wennerholm 2019 explicitly reported on the absence of blinding for outcome assessors (caregivers) and was thus rated as high risk of bias.

As above, measurement of objective outcomes such as perinatal death is unlikely to be influenced by lack of blinding.

Incomplete outcome data

We considered the majority of trials (24) (Augensen 1987; Baev 2017; Bergsjo 1989; Breart 1982; Chanrachkul 2003; Dyson 1987; Gelisen 2005; Grobman 2018; Hannah 1992; Heimstad 2007; Henry 1969; Herabutya 1992; James 2001; Keulen 2019; Martin 1989; Miller 2015; NICHHD 1994; Nielsen 2005; Ocon 1997; Roach 1997; Sahraoui 2005; Walker 2016; Wennerholm 2019; Witter 1987) to be at low risk of attrition bias, with minimal/no losses to follow‐up or exclusions. We judged seven trials to be at unclear risk of attrition bias (Brane 2014; Chakravarti 2000; Cohn 1992; Cole 1975; Egarter 1989; Sargunam 2019; Suikkari 1983), commonly due to some post‐randomisation exclusions and/or missing data, or due to insufficient information to determine losses or exclusions (due to publication in abstract form only).

We judged three trials to be at high risk of attrition bias. In both Martin 1978 and Tylleskar 1979, between 25% and 30% of the women randomised were excluded post‐randomisation due to going into labour prior to their planned date of induction (for women in the induction group), due to obstetric abnormalities or failure to go into spontaneous labour before 42 weeks (women in the expectant management group of Martin 1978), going into labour prior to their expected delivery date (women in the expectant management group of Tylleskar 1979). In Sande 1983, a per protocol analysis was performed, where women were not analysed in the group to which they were randomised, rather according to whether they had their labour induced, or delivered spontaneously.

Selective reporting

Only five trials (Grobman 2018; Keulen 2019; Sargunam 2019; Walker 2016; Wennerholm 2019) were judged to be at low risk of reporting bias, with outcomes reported as prespecified in the published protocol. We judged 23 trials (Baev 2017; Brane 2014; Breart 1982; Chakravarti 2000; Chanrachkul 2003; Cohn 1992; Cole 1975; Dyson 1987; Gelisen 2005; Hannah 1992; Heimstad 2007; Henry 1969; Herabutya 1992; James 2001; Martin 1978; Miller 2015; NICHHD 1994; Nielsen 2005; Ocon 1997; Roach 1997; Sahraoui 2005; Suikkari 1983; Witter 1987) to be at unclear risk of reporting bias, largely due to insufficient information to assess selective reporting (i.e. no access to trial protocols and limited detail reported in manuscript methods). We considered six trials (Augensen 1987; Bergsjo 1989; Egarter 1989; Martin 1989; Sande 1983; Tylleskar 1979), to be at high risk of reporting bias, predominately due to the incomplete reporting of outcomes data (such as in text or figures only, with statements such as "no significant difference between groups" made) such that outcome data could not be included in review meta‐analyses.

Other potential sources of bias

Most of the trials (25) (Augensen 1987; Baev 2017; Bergsjo 1989; Brane 2014; Breart 1982; Chanrachkul 2003; Cole 1975; Dyson 1987; Gelisen 2005; Grobman 2018; Hannah 1992; Heimstad 2007; Henry 1969; Herabutya 1992; James 2001; Martin 1989; Miller 2015; NICHHD 1994; Ocon 1997; Roach 1997; Sahraoui 2005; Sargunam 2019; Walker 2016; Wennerholm 2019; Witter 1987), appeared to be free of other potential sources of bias. We judged the other nine trials to be at unclear risk of bias, five trials due to limited reporting (abstract only or limited methodological detail provided) (Chakravarti 2000; Cohn 1992; Martin 1978; Suikkari 1983; Tylleskar 1979); one trial each for imbalance in the numbers of women randomised to each group (Egarter 1989), baseline characteristic imbalance (Nielsen 2005), lack of reporting of baseline characteristics (Sande 1983), and the systematically different care and assessment of neonates between groups (with the induction group receiving obstetrician‐led intrapartum secondary care, and a high proportion of the expectant management group receiving midwifery‐led primary care at both the start of labour and time of birth (Keulen 2019).

Effects of interventions

See: Table 1; Table 3

Labour induction versus expectant management (all trials)

Primary outcome

Perinatal death

Fewer perinatal deaths occurred in the labour induction groups than in the expectant management groups: four perinatal deaths occurred in the induction group compared with 25 in the expectant group: risk ratio (RR) 0.31, 95% confidence interval (CI) 0.15 to 0.64; 22 trials; 18,795 infants; high‐certainty evidence; Analysis 1.1.

1.1 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 1: Perinatal death

Interaction tests failed to demonstrate differences between the timing of induction subgroups for perinatal deaths (Chi² = 0.62, P = 0.73, I² = 0%; Analysis 2.1); parity (Chi² = 0.08, P = 0.77, I² = 0%; Analysis 3.1); or for subgroups according to state of cervix (Chi² = 0.01, P = 0.99, I² = 0%; Analysis 4.1). Rates of perinatal death by gestation are also presented in Table 7.

2.1 — Comparison 2: Labour induction versus expectant management (subgroup analysis by gestational age at induction), Outcome 1: Perinatal death

3.1 — Comparison 3: Labour induction versus expectant management (subgroup analysis by parity), Outcome 1: Perinatal death

4.1 — Comparison 4: Labour induction versus expectant management (subgroup analysis by status of cervix), Outcome 1: Perinatal death

4. Rates of perinatal death by gestation.

Week	IOL		Expectant
		rate/1000		rate/1000
37	0	0	0	0
38	0/111	0	1/117	8.5
39	2/3455	0.6	4/3443	1.2
40‐41	0/380	0	1/380	2.6
≥ 42	2/5472	0.37	19/5437	3.5

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^IOL:^{induction of labour}

Two trials reported perinatal death by parity ‐ Keulen 2019 reported three stillbirths (one in a nulliparous woman and one in a multiparous woman in the expectant management group; and one in a multiparous woman in the induction group); and in Wennerholm 2019 all six perinatal deaths (five stillbirths and one neonatal death) occurring in the expectant management group in nulliparous women.

Some trials (e.g. Hannah 1992), excluded perinatal deaths due to congenital anomalies while other trials included these. If the three deaths reported to be due to congenital anomalies in other trials were excluded, there were then a total of three deaths in the labour induction group and 23 in the expectant management group. This made little difference to the overall result (RR 0.30, 95% CI 0.14 to 0.64).

Table 2 details, where known, the respective causes of death (stillbirths and neonatal deaths) for 19 babies, including the stillbirth reported in Martin 1978 (where it was not clear if there were any neonatal deaths).

The number needed to treat for an additional beneficial outcome (NNTB) with a policy of induction of labour in order to prevent one perinatal death was 544 (95% CI 441 to 1042).

Twelve trials, (Baev 2017; Brane 2014; Breart 1982; Chakravarti 2000; Cohn 1992; Miller 2015; Nielsen 2005; Ocon 1997; Roach 1997; Sargunam 2019; Tylleskar 1979; Witter 1987), did not report on perinatal deaths.

Sensitivity analyses

Only 10 of the 34 trials were judged to be of low risk of bias, defined as adequate allocation concealment and low attrition (Baev 2017; Grobman 2018; Hannah 1992; Heimstad 2007; Keulen 2019; Miller 2015; NICHHD 1994; Nielsen 2005; Walker 2016; Wennerholm 2019). We have presented each of the sensitivity analyses under each of the relevant prespecified outcomes.

Perinatal death ‐ sensitivity analysis: RR 0.29, 95% CI 0.10 to 0.83; seven trials, 15,539 infants. There were three perinatal deaths in the induction group and 14 perinatal deaths in the expectant management group. This sensitivity analysis was similar to the overall analysis (RR 0.31, 95% CI 0.15 to 0.64), favouring induction over expectant management.

Secondary outcomes for the infant/child

Stillbirth

Eighteen of the 25 perinatal deaths were stillbirths. Two stillbirths occurred in the induction group and 16 stillbirths occurred in the expectant management group (RR 0.30, 95% CI 0.12 to 0.75; 22 trials; 18,795 infants; high‐certainty evidence; Analysis 1.2). Interaction tests failed to demonstrate differences between the timing of induction subgroups (Chi² = 0.49, P = 0.78, I² = 0%; Analysis 2.2) or for subgroups according to by parity (Chi² = 0.13, P = 0.72, I² = 0%; Analysis 3.2) or state of cervix (Chi² = 0.01, P = 0.99, I² = 0%; Analysis 4.2) for the outcome of stillbirth.

1.2 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 2: Stillbirth

2.2 — Comparison 2: Labour induction versus expectant management (subgroup analysis by gestational age at induction), Outcome 2: Stillbirth

3.2 — Comparison 3: Labour induction versus expectant management (subgroup analysis by parity), Outcome 2: Stillbirth

4.2 — Comparison 4: Labour induction versus expectant management (subgroup analysis by status of cervix), Outcome 2: Stillbirth

Sensitivity analyses

Stillbirth ‐ sensitivity analysis: RR 0.27, 95% CI 0.08 to 0.98; seven trials, 15,539 infants, with two stillbirths in the induction group and 10 stillbirths in the expectant management group. This sensitivity analysis was similar to the overall analysis (RR 0.30, 95% CI 0.12 to 0.75), favouring induction over expectant management.

Neonatal death

There were 11 live birth deaths ‐ two of these were in the induction group and nine were in the expectant management groups (RR 0.39, 95% CI 0.13 to 1.14; 21 trials; 18,611 infants; Analysis 1.3).

1.3 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 3: Neonatal death

Birth asphyxia

Rates of birth asphyxia were not clearly different between the induction and expectant management groups (RR 1.66, 95% CI 0.61 to 4.55: four trials; 1456 infants; Analysis 1.4).

1.4 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 4: Birth asphyxia

Admission to neonatal intensive care unit (NICU)

Rates of NICU admissions were lower when labour induction was compared with expectant management (RR 0.88, 95% CI 0.80 to 0.96; 17 trials; 17,826 infants; high‐certainty evidence; Analysis 1.5).

1.5 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 5: Admission to neonatal intensive care unit

Interaction tests failed to demonstrate differences between the timing of induction subgroups (Chi² = 1.67, P = 0.43, I² = 0%; Analysis 2.3) or for subgroups according to parity (Chi² = 2.03, P = 0.36, I² = 1.4%; Analysis 3.3) or state of cervix (Chi² = 0.81, P = 0.67, I² = 0%; Analysis 4.3) for the outcome of NICU admission.

2.3 — Comparison 2: Labour induction versus expectant management (subgroup analysis by gestational age at induction), Outcome 3: Admission to neonatal intensive care unit

3.3 — Comparison 3: Labour induction versus expectant management (subgroup analysis by parity), Outcome 3: Admission to neonatal intensive care unit

4.3 — Comparison 4: Labour induction versus expectant management (subgroup analysis by status of cervix), Outcome 3: Admission to neonatal intensive care unit

Sensitivity analyses

Admission to the NICU ‐ sensitivity analysis: RR 0.87, 95% CI 0.79 to 0.96; nine trials, 15,709 infants. This was very similar to the overall analysis (RR 0.88, 95% CI 0.80 to 0.96).

Neonatal convulsions

There were no clear differences in instances of neonatal convulsions when labour induction was compared with expectant management (average RR 1.01, 95% CI 0.15 to 6.67; Tau² = 2.25; Chi² = 7.96, P = 0.05; I² = 62%; 5 trials, 13,216 infants; Analysis 1.6). The heterogeneity may be due to Grobman 2018 (who reported seizures).

1.6 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 6: Neonatal convulsions

Neonatal encephalopathy (HIE)

Two trials reported neonatal encephalopathy (HIE), indicating little or no difference between the induction and expectant groups (RR 0.69, 95% CI 0.37 to 1.31; 8851 infants; low‐certainty evidence; Analysis 1.7).

1.7 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 7: Neonatal encephalopathy (HIE)

Use of anticonvulsants

No clear differences between induction and expectant groups were evident for use of anticonvulsants in a single trial (RR 0.34, 95% CI 0.01 to 8.17; 349 infants; Analysis 1.8).

1.8 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 8: Use of anticonvulsants

Meconium aspiration syndrome

There was a 25% relative reduction in the risk of meconium aspiration syndrome in the induction groups compared with the expectant management groups (RR 0.75, 95% CI 0.62 to 0.92; 13 trials; 16,622 infants; Analysis 1.9).

1.9 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 9: Meconium aspiration syndrome

Pneumonia

In two trials, there was a possibly decreased incidence of pneumonia in the induction group compared with the expectant management group (RR 0.54, 95% CI 0.27 to 1.06; 8851 infants; Analysis 1.10).

1.10 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 10: Pneumonia

Apgar score less than seven at five minutes

Probably fewer babies had Apgar scores less than seven at five minutes in the induction groups compared with the expectant management groups (RR 0.73, 95% CI 0.56 to 0.96; 20 trials; 18,345 infants; moderate‐certainty evidence; Analysis 1.11). Several trials reported different cut‐offs for Apgar scores but omission of these results made little difference to the overall result.

1.11 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 11: Apgar score less than 7 at 5 minutes

Birthweight (g)

On average, infants born to mothers in the induction group had lower birthweights than those born to mothers in the expectant management group (mean difference (MD) ‐59.38 g, 95% CI ‐77.03 to ‐41.73; 18 trials; 8817 infants; Analysis 1.12).

1.12 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 12: Birthweight (g)

Grobman 2018 reported birthweights as median and interquartile ranges (IQR), also showing lower birthweights in the induction group (median 3330 g IQR 3040 to 3565) compared with the expectant management group (median 3380 g IQR 3110 to 3650); P < 0.001.

Birthweight greater than 4000 g

There was a 28% relative reduction in the rate of macrosomia (greater than 4000 g) in the labour induction groups (average RR 0.72, 95% CI 0.54 to 0.96; 8 trials; 5593 infants; Tau² = 0.09; Chi² = 20.84, P = 0.004; I² = 66%; Analysis 1.13) (Hannah 1992 used a cutoff‐of 4500 g rather than 4000 g for this outcome). Removal of Gelisen 2005 from the analysis for this outcome (which still observed a substantial beneficial effect, with 23/300 macrosomic infants born to women in the induction group, versus 74/300 infants to women in the expectant management group), eliminated the observed heterogeneity.

1.13 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 13: Birthweight > 4000 g

Neonatal (birth) trauma

Meta‐analysis of data from five trials suggests that induction makes little or no differencein rates of birth trauma in newborns and expectant management (RR 0.97, 95% CI 0.63 to 1.49; 13,106 infants; moderate‐quality evidence; Analysis 1.14).

1.14 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 14: Neonatal (birth) trauma

Unreported outcomes

No trials reported on neurodevelopment at childhood follow‐up (although Bergsjo 1989 reported no signs of neurological impairment in children at two years of age).

Secondary outcomes for the mother

Caesarean section

There were probably fewer caesarean sections (a relative reduction of 10%) in the induction groups compared with the expectant management groups on meta‐analysis of data from 31 trials (RR 0.90, 95% CI 0.85 to 0.95; 21,030 women; moderate‐certainty evidence; Analysis 1.15). This equates to a reduction of nearly 2% (from a rate of 18.6% in the expectant management group to 16.7% in the induction group). Subgroup interaction tests did not show clear differences according to timing of induction (Chi² = 3.70, P = 0.16, I² = 45.9%; Analysis 2.4), by parity (Chi² = 1.84, P = 0.40, I² = 0%; Analysis 3.4) or by state of cervix (Chi² = 1.60, P = 0.45, I² = 0%; Analysis 4.4) for this outcome.

1.15 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 15: Caesarean section

2.4 — Comparison 2: Labour induction versus expectant management (subgroup analysis by gestational age at induction), Outcome 4: Caesarean section

3.4 — Comparison 3: Labour induction versus expectant management (subgroup analysis by parity), Outcome 4: Caesarean section

4.4 — Comparison 4: Labour induction versus expectant management (subgroup analysis by status of cervix), Outcome 4: Caesarean section

Sensitivity analyses

Caesarean section sensitivity analysis: RR 0.90, 95% CI 0.84 to 0.96; 10 trials, 16,075 women. These results are very similar to the overall analysis (RR 0.90, 95% CI 0.85 to 0.95).

Operative vaginal birth (forceps or ventouse)

Rates of operative vaginal birth showed little or no difference between the policy of labour induction and expectant management groups (RR 1.03, 95% CI 0.96 to 1.10; 22 trials, 18,584 women; moderate‐certainty evidence; Analysis 1.16). This equates to an increase of 0.4% (from a rate of 13.6% in the expectant management group to 14% in the induction group). Subgroup interaction tests did not show clear differences according to timing of induction (Chi² = 1.14, P = 0.57, I² = 0%; Analysis 2.5), parity (Chi² = 1.62, P = 0.44, I² = 0%; Analysis 3.5) or by state of cervix (Chi² = 0.73, P = 0.70, I² = 0%; Analysis 4.5) for this outcome.

1.16 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 16: Operative vaginal birth (forceps or ventouse)

2.5 — Comparison 2: Labour induction versus expectant management (subgroup analysis by gestational age at induction), Outcome 5: Operative vaginal birth (forceps or ventouse)

3.5 — Comparison 3: Labour induction versus expectant management (subgroup analysis by parity), Outcome 5: Operative vaginal birth (forceps or ventouse)

4.5 — Comparison 4: Labour induction versus expectant management (subgroup analysis by status of cervix), Outcome 5: Operative vaginal birth (forceps or ventouse)

Sensitivity analyses

Operative vaginal birth sensitivity analysis: RR 0.99, 95% CI 0.92 to 1.07; 8 trials, 15,565 women. This was similar to the overall analysis (RR 1.03, 95% CI 0.96 to 1.10).

Analgesia used

There was little or no difference in the use of epidural/regional analgesia between induction and expectant management groups (average RR 1.09, 95% CI 0.99 to 1.20; 8 trials, 4579 women; Tau² = 0.01; Chi² = 24.41, P = 0.001; I² = 71%) (Analysis 1.17). A possible increased use of analgesia (variously defined) was observed with labour induction, compared with expectant management (average RR 1.11, 95% CI 1.05 to 1.18; 4 trials, 2352 women) (Analysis 1.17).

1.17 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 17: Analgesia used

Perineal trauma

Probably little or no difference in perineal trauma, assessed as severe perineal tear, was seen between induction and expectant management (RR 1.04, 95% 0.85 to 1.26; 5 trials; 11,589 women; low‐certainty evidence (Analysis 1.18). For episiotomy (RR 0.96, 95% CI 0.84 to 1.11; 2 trials; 1747 women; and obstetrical and sphincter injuries (RR 0.81, 95% CI 0.51 to 1.31; 2 trials; 1698 women) there were probably little or no differences between induction and expectant management (Analysis 1.18).

1.18 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 18: Perineal trauma

Interaction tests, performed for perineal trauma (assessed as severe perineal tear), failed to detect any differences for subgroups by timing of induction (Chi² = 1,89, P = 0.17, I² = 47.2% Analysis 2.6), by parity (Chi² = 1.89, P = 0.17, I² = 47.2%; Analysis 3.6) or by state of cervix (tests for subgroup differences: not applicable) for this outcome.

2.6 — Comparison 2: Labour induction versus expectant management (subgroup analysis by gestational age at induction), Outcome 6: Perineal trauma

3.6 — Comparison 3: Labour induction versus expectant management (subgroup analysis by parity), Outcome 6: Perineal trauma (severe perineal tear)

Sensitivity analyses

Sensitivity analysis for perineal trauma (severe perineal tear): all five trials reporting this outcome were judged to not be at high risk of bias and so the sensitivity analysis is the same as the overall analysis.

Prolonged labour

The outcome of prolonged labour was reported in several different ways by four trials with 1009 women, with none of the four comparisons showing clear differences between the induction and expectant management groups (Analysis 1.19).

1.19 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 19: Prolonged labour

Postpartum haemorrhage

There was probably no or little difference in rates of postpartum haemorrhage (variously defined) for induction and expectant management groups (RR 1.02, 95% CI 0.91 to 1.15; 9 trials, 12,609 women; moderate‐certainty evidence; Analysis 1.20).

1.20 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 20: Postpartum haemorrhage

Breastfeeding

There was probably no or little differences between induction and expectant groupsfor breastfeeding (at discharge in one trial; and at four to eight weeks after discharge in the other trial) (RR 1.00, 95% CI 0.96 to 1.04; 7487 infants; moderate‐certainty evidence ‐ Analysis 1.21).

1.21 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 21: Breastfeeding

Maternal satisfaction

In one trial of 496 women, more women in the induction group said that they would choose the same arm in a future trial compared with women in the expectant management group (RR 1.93, 95% CI 1.62 to 2.30), but in two other trials, similar numbers of women indicated that they preferred the group they had been allocated to (RR 0.99, 95% CI 0.88 to 1.13; 493 women; Analysis 1.22). Sargunam 2019 also reported little or no difference in satisfaction with pregnancy outcomes between groups (RR 0.92 95% CI 0.80 to 1.06; 308 women; Analysis 1.22). Walker 2016 reported little or no difference in Childbirth Experience Questionnaire scores (four‐point scale; higher scores indicate higher satisfaction) between women in the induction or expectant management groups (MD 0.07, 95% CI ‐0.02 to 0.16; 619 women; Analysis 1.23).

1.22 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 22: Maternal satisfaction

1.23 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 23: Maternal satisfaction

Grobman 2018 also reported slightly higher scores on the Labor Agentry Scale, indicating greater perceived control during childbirth in the induction group; and also reported that women in the induction group reported less pain than women in the expectant management group.

Unreported outcomes

No trials reported on anxiety before birth or postnatal depression.

Secondary outcomes relating to health service use

Length of maternal postnatal stay (days)

It is very uncertain whether there is any difference between induction or expectant management for duration of maternal hospital stay (average MD ‐0.19 days, 95% CI ‐0.56 to 0.18; 7 trials; 4120 women; very low‐quality evidence; Analysis 1.24). There was very substantial heterogeneity (Tau² = 0.20; Chi² = 104.20, P < 0.00001; I² = 94%) between the trials for this outcome.

1.24 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 24: Length of maternal hospital stay (days)

Length of maternal postnatal stay (days, categories)

One trial of 6091 women reported five maternal postnatal stay categories (Grobman 2018) indicating slightly more women in the induction group stayed two days and slightly fewer women in the induction group stayed 3 or 4 days (Analysis 1.25).

1.25 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 25: Length of maternal (postnatal) stay (categories)

Length of neonatal hospital stay (days)

In one trial of 302 babies, there was a slightly shorter mean hospital stay for the induction group compared with the expectant management group (MD ‐0.30 days, 95% CI ‐0.61 to 0.01; Analysis 1.26).

1.26 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 26: Length of neonatal hospital stay (days)

Length of neonatal postnatal stay (days, categories)

One trial of 6091 infants reported length of neonatal postnatal stay as five categories, which we collapsed into ≤ 2 days and ≥ 3 days. Infants in the induction group were more likely to stay ≤ 2 days than those in the expectant group (RR 1.05, 95% CI 1.02 to 1.08) and correspondingly less likely to stay ≥ 3 days (RR 0.86, 95% CI 0.79 to 0.94) (Analysis 1.27).

1.27 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 27: Length of neonatal (postnatal) stay (categories)

Length of labour (hours)

Overall, length of labour was shorter for women undergoing induction compared with expectant management (average MD ‐1.08 hours, 95% CI ‐1.67 to ‐0.50; 12 trials; 4025 women; Tau² = 0.84; Chi² = 46.70, P < 0.0001; I² = 72%; Analysis 1.28).

1.28 — Comparison 1: Labour induction versus expectant management (all trials), Outcome 28: Length of labour (hours)

Funnel plots

We assessed funnel plots for the outcomes: perinatal death (Figure 4), stillbirth (Figure 5), neonatal death (Figure 6), admission to NICU (Figure 7), meconium aspiration syndrome (Figure 8), Apgar score less than seven at five minutes (Figure 9), birthweight (Figure 10), caesarean section (Figure 11), operative vaginal birth (Figure 12), postpartum haemorrhage (Figure 13) and length of labour (Figure 14).

Funnel plot of comparison: 1 Labour induction versus expectant management (all trials), outcome: 1.1 Perinatal death.

Funnel plot of comparison: 1 Labour induction versus expectant management (all trials), outcome: 1.2 Stillbirth.

Funnel plot of comparison: 1 Labour induction versus expectant management (all trials), outcome: 1.3 Neonatal death.

Funnel plot of comparison: 1 Labour induction versus expectant management (all trials), outcome: 1.5 Admission to neonatal intensive care unit.

Funnel plot of comparison: 1 Labour induction versus expectant management (all trials), outcome: 1.9 Meconium aspiration syndrome.

Funnel plot of comparison: 1 Labour induction versus expectant management (all trials), outcome: 1.11 Apgar score less than 7 at 5 minutes.

Funnel plot of comparison: 1 Labour induction versus expectant management (all trials), outcome: 1.12 Birthweight (g).

Funnel plot of comparison: 1 Labour induction versus expectant management (all trials), outcome: 1.15 Caesarean section.

Funnel plot of comparison: 1 Labour induction versus expectant management (all trials), outcome: 1.16 Operative vaginal birth (forceps or ventouse).

Funnel plot of comparison: 1 Labour induction versus expectant management (all trials), outcome: 1.20 Postpartum haemorrhage.

Funnel plot of comparison: 1 Labour induction versus expectant management (all trials), outcome: 1.28 Length of labour (hours).

Some visual asymmetry may be apparent for meconium aspiration syndrome (Figure 8); birthweight (Figure 10) and postpartum haemorrhage (Figure 13). Funnel plots for perinatal death (Figure 4), stillbirth (Figure 5), and neonatal death (Figure 6) were difficult to visually interpret.

Discussion

Summary of main results

In this updated review, we included 34 randomised controlled trials (reporting on 21,563 women).

We included pregnant women at or beyond 37 weeks' gestation. Since a risk factor at this stage of pregnancy would normally require an intervention, only trials including women at low risk for complications were eligible. We accepted the trialists' definition of 'low risk'. The trials of induction of labour in women with prelabour rupture of membranes at or beyond 37 weeks were not considered in this review.

A policy of labour induction reduced perinatal deaths (with four perinatal deaths in the labour induction policy group compared with 25 perinatal deaths in the expectant management group) (high‐certainty evidence). When restricted to a policy of induction at later gestational ages (> 41 weeks), there were two and 13 perinatal deaths, respectively. While subgroup interaction tests did not have sufficient power to assess whether perinatal mortality differed by week of gestation, the rate of perinatal deaths in the expectant management compared to the induction group for gestational age > 42 weeks, 3.5 deaths per 1000, was higher than the rate of perinatal deaths for gestational age 40 to 41 weeks (2.6 deaths per 1000) and 39 weeks (1.2 deaths per 1000); see Table 7.

Although some trials excluded deaths from congenital anomalies, other trials did not exclude these deaths. When the three deaths reported to be due to congenital anomalies were excluded, the overall findings remained very similar. Induction of labour also reduced stillbirth compared with expectant management (two versus 16 in the expectant management group), (high‐certainty evidence).

A policy of labour induction probably reduced caesarean section compared with expectant management (moderate‐certainty evidence) and probably had no or little impact on operative vaginal birth compared with expectant management (moderate‐certainty evidence). Induction of labour also reduced neonatal intensive care unit admission (high‐certainty evidence), and probably reduced the occurrence of Apgar scores less than seven at five minutes (moderate‐certainty evidence), compared with expectant management. Induction of labour probably made no or little difference for neonatal trauma, postpartum haemorrhage and breastfeeding compared with expectant management (moderate‐certainty evidence); and may lead to no or little difference in neonatal encephalopathy and perineal trauma (low‐certainty evidence). The effect of labour induction compared with expectant management on length of maternal hospital stay was uncertain (very low‐certainty evidence). Neurodevelopment at childhood follow‐up and postnatal depression were not reported by any of the included trials.

No clear differences by timing of induction (< 40 weeks versus 40 to 41 weeks versus > 41 weeks), cervical status (favourable versus unfavourable versus mixed), or parity (nulliparous versus multiparous versus mixed) were apparent in subgroup analyses for the main outcomes of this review.

For the sensitivity analyses, all six prespecified outcomes demonstrated results in the same direction as the main analyses and there was little material difference in the overall result.

This review evaluates trials where a policy of induction has been compared with a policy of waiting. However, women scheduled to be induced may not have ended up being induced; and women allocated to wait may have ended up being induced (Keirse 2010). For example, about one‐third of the women randomised to the induction policy group in the Hannah trial were not induced; and about one‐third of the women randomised to waiting or expectant management were induced (Hannah 1992).

Overall completeness and applicability of evidence

The body of evidence for this review is now quite extensive, including 34 trials and over 20,000 women. This has been sufficient to detect a difference in perinatal death between the induction and expectant management groups. The decrease seen in caesarean section with a policy of induction has been previously questioned by some authors (Keirse 2010; Mandruzzato 2010). They have suggested that the women in the large Hannah 1992 trial who were induced in the policy of induction group (66% of this group), may have had a more effective cervical ripening regimen (prostaglandin) than the women who were induced in the expectant management group (33% of this group), and that more women in the expectant management group had a caesarean section for fetal distress (8.3% versus 5.7% in the induction group) (Keirse 2010;Mandruzzato 2010). Since review results for caesarean section were similar when the Hannah 1992 trial was omitted, this is not likely to have been the reason for the effect observed.

The trials included in this review employed a wide range and combinations of induction methods (see Characteristics of included studies), and it was not possible to assess differences in outcomes by method of induction through conducting subgroup analyses. Trials were conducted in different countries and consequently this review reflects a range of strategies for both induction of labour, and expectant management, across trials.

Some women with post‐term pregnancies have described this period of unexpected waiting as being in a state of limbo, with increasingly negative feelings as the pregnancy continues, which could be addressed with more information and support from their healthcare professionals (Wessberg 2017). Our review highlighted the lack of information measured and reported by randomised trials to date, with only five (Grobman 2018; Heimstad 2007; Martin 1978; Sargunam 2019; Walker 2016) of the 34 included studies reporting some measure of maternal satisfaction. A recent systematic review of qualitative evidence included five studies addressing women's experiences and perceptions of induction of labour for uncomplicated post‐term pregnancy, highlighting the importance of women's understanding of induction in influencing their choices, decision‐making, and thus satisfaction ‐ and emphasised the need for "in‐depth and clear unbiased individualized information and education on alternatives and details of procedures as well as risks and benefits" (Akuamoah‐Boateng 2018).

As noted above, the randomised trials conducted to date have not provided data regarding longer‐term neurodevelopmental outcomes for children, and cohort studies have shown inconsistent results as to whether post‐term birth has a negative, positive or null impact on childhood development. A large cohort study from Denmark has suggested that more children born at 41 weeks' gestation or later achieved developmental milestones compared with children born at earlier term gestations (39 to 40 weeks) (Olesen 2015). A further large cohort study from Australia demonstrated elevated risks of poor child development at school age with early (at < 39 weeks' gestation) planned birth compared with birth at later gestations (Bentley 2016).

Assessment of intervention cost‐effectiveness was beyond the scope of our review, however, three of the included trials have reported data related to costs. In the Hannah 1992 trial, the mean cost of a woman undergoing induction for a post‐term pregnancy was $193 lower than for a woman managed expectantly, due mainly to the costs of additional monitoring and the significantly higher rates of caesarean section among women assigned to expectant management. Walker 2017 reported that induction of labour at 39 weeks, specifically for nulliparous women aged 35 years and over, is associated with a mean cost saving of £263 and a small additional gain in QALYs (without considering QALY gains from stillbirth prevention). A health utilisation study (based on the Grobman 2018 trial) (Grobman 2020) found that while low risk nulliparous women, assigned to induction of labour at 39⁰ to 39⁴ weeks spent more time on the labour and delivery suite (thus using more resources specific to induction), they had fewer antenatal visits and tests, fewer intrapartum interventions, and shorter postnatal stays, compared with women assigned to expectant management; and concluded "that the health outcome advantages associated with induction of labour are gained without incurring uniformly greater health care resource use".

Quality of the evidence

Included trials were generally at low to moderate risk of bias. Aspects of methodological quality were unclear for many of the included trials (Figure 2; Figure 3).

Most of the outcomes assessed using GRADE had a rating of high‐ or moderate‐certainty evidence (see Table 1; Table 3) ‐ with downgrading decisions generally due to study limitations such as risk of selection bias, or imprecise effect estimates. Postpartum haemorrhage was downgraded to moderate due to indirectedness.

However, for the majority of outcomes assessed using GRADE, statistical heterogeneity was mostly low, countering claims (e.g. Davey 2016), that some of the trials had unreliable results due to being outdated or flawed. One outcome (length of maternal stay) was downgraded to very low‐certainty evidence (due to inconsistency) and two outcomes (neonatal encephalopathy and perineal trauma (severe perineal tear)) were downgraded for imprecision.

Potential biases in the review process

Due to the rigorous methods used (comprehensive searching, double screening and data extraction, and careful appraisal and analysis), biases are likely to be low.

As mentioned above, there have been several criticisms of trials and reviews on this topic. Wood 2014 and colleagues point out that the decision to perform a caesarean section is often subjective, and anxiety from medical staff about the dangers of a prolonged pregnancy may be a factor in determining when to carry out a caesarean, as could factors such as fetal distress or fetal size. They also make the observation, whatever the reason(s) may be, that this does not change the fact that induction has shown reduced risk of caesarean section in clinical trials of induction of labour versus expectant management in women with intact membranes.

We investigated reporting biases (such as publication bias) using funnel plots for prespecified outcomes, with a small number demonstrating some asymmetry. This could indicate possible reporting bias, with the smaller published trials reporting exaggerated intervention effect estimates, and there remains the possibility that further small trials (including those reporting smaller effect estimates) remain unpublished.

Agreements and disagreements with other studies or reviews

Both observational studies and systematic reviews of randomised controlled trials of timing of induction have shown mixed findings for important outcomes including perinatal death and caesarean section rates (Davey 2016).

Wood 2014 is the most comparable systematic review and meta‐analysis in terms of included studies, though they only reported a single outcome, caesarean section. Across 27 trials in women between 37 and 42 weeks' gestation, they found a similar reduction with a policy of induction as our review. The Mishanina 2014 systematic review and meta‐analysis of induction versus expectant management at any gestational age also found a reduction in caesarean birth for inductions from 37 weeks onwards (but not if induction was at less than 37 weeks), along with an overall reduction in fetal death with induction. The recent Saccone 2019 systematic review and meta‐analysis, included only seven trials (7598 women) in women with uncomplicated singleton pregnancies at term (defined as 39⁰ to 40⁶ weeks) ‐ all seven trials were included in our review. While the authors did not demonstrate reductions in the risks of caesarean section or perinatal death as we have, they stated that they recognised the review was not powered for these outcomes. The Sotiriadis 2019 systematic review and meta‐analysis including women with singleton uncomplicated pregnancies, randomised between 39⁰ and 39⁶ weeks) ‐ a 'subset' of the Saccone 2019 review. Sotiriadis 2019 did demonstrate a reduction in caesarean section as was observed in our review. The difference in findings between Saccone 2019 and Sotiriadis 2019 appear to be largely attributable to the high rate of caesarean section in the induction group in the Miller 2015 trial (25/82 in induction group versus 14/79 in expectant group) (included in Saccone 2019 but not Sotiriadis 2019), which randomised women with an unfavourable cervix at 38⁰ to 38⁶ weeks.

Recent mathematical modelling (Monte Carlo microsimulation) has revealed similar findings to our review, however specifically in relation to nulliparous women at 39 weeks with uncomplicated, singleton, vertex pregnancies (Sinkey 2018). Maternal and neonatal risks (including caesarean section, maternal morbidity, stillbirth, neonatal death and neonatal morbidity) were lower with induction of labour, as compared with expectant management, including induction at 41 weeks if a woman has still not given birth (Sinkey 2018). The Keulen 2018 review was conducted specifically to focus on studies of comparisons of induction within the 41 to 42 weeks' gestation timeframe, to assess the outcomes of perinatal mortality, meconium aspiration syndrome and caesarean section. Only four trials were considered to have comparisons relevant to this timing of induction, and the authors concluded that evidence for the recommendation to induce labour at 41 weeks instead of 42 weeks for improved perinatal outcomes was lacking (Keulen 2018).

While a major concern surrounding elective induction at > 37 weeks, particularly in first pregnancies, has been increased risk of caesarean section (Davey 2016), such studies have been largely observational in nature, and increasingly, there is evidence to the contrary (Souter 2019). In a recent scoping review of clinical indications for induction, 15 studies related to induction of labour for post‐term pregnancy (> 40 weeks) were identified; this included the previous version of our review (Middleton 2018), the Keulen 2018 review, the Keulen 2019 trial, and 12 observational studies (one prospective cohort, nine retrospective cohorts, and two secondary analyses of cohort studies) (Coates 2020). Based on the totality of evidence, the authors concluded that induction of labour beyond 41 to 42 weeks was associated with reductions in perinatal death and caesarean section, though recognising the high NNT for perinatal death.

While the subgroup interaction tests for our main outcomes (perinatal death, stillbirth, admission to NICU, caesarean section, operative vaginal birth, perinatal trauma) did not demonstrate any clear differential effects of induction based on gestational age (< 40 weeks, 40 to 41 weeks, > 41 weeks), over 72% of perinatal deaths reported were in the > 41 week subgroup.

In addition to factors explored in our review's subgroup analysis (gestational age, parity, cervical status), there are various other factors that are likely to impact outcomes following induction (and may explain some discrepancies observed between studies), such as indications for caesarean section, and maternal age. For example, in an Australian retrospective cohort study (17,647 women), among nulliparous women, induction of labour at 38 to 39 weeks was shown to be associated with an increased risk of caesarean section in young women (< 25 years of age), but not associated with caesarean section for slow progress (De Vries 2019). Conversely, induction of labour at 38 to 39 weeks was associated with an increased risk of caesarean section for suspected fetal compromise among nulliparous women < 30 years (De Vries 2019). In a retrospective registry‐based study from Denmark, Finland, Iceland, Norway and Sweden (involving 3,398,586 births), advanced maternal age was associated with an increased risk of caesarean section among women undergoing induction of labour at term with singleton pregnancies without previous caesarean sections; with the absolute risk being three to five times higher across five‐year age groups in nulliparous relative to multiparous women (Bergholt 2020). It is important, however, to distinguish between different methodological approaches where comparing labour induction to spontaneous onset of labour in a retrospective cohort (instead of a prospective assessment of expectant management of pregnancy) which may lead to exaggerated estimates of the risk of caesarean birth, for example (Danilack 2016). Moreover, in our review, there did not appear to be any differential effect of caesarean section by baseline rates of studies.

Many of the current relevant clinical practice guidelines recommend offering women induction of labour after 41 completed weeks of gestation (ACOG 2014; New Zealand Guideline Development Panel 2019; NICE 2008; SOGC 2017; WHO 2018). The most recent WHO guidelines provide a recommendation for induction of labour for women who are known with certainty to have reached 41 weeks; they highlight that the guidance does not apply to settings where gestational age cannot be reliably established and the importance of discussing the potential need for induction with women in advance to provide opportunity for women to understand benefits and possible risks (WHO 2018). These guidelines were based on the previous version of this review (Middleton 2018), in which the evidence for some critical outcomes (including perinatal death, stillbirth, admission to the neonatal intensive care) were judged to be of lower certainty than this update which incorporates new evidence of higher certainty.

Authors' conclusions

Implications for practice.

The main message from this review is that a policy of induction of labour at or beyond term is associated with fewer perinatal deaths, including stillbirths (although the absolute risk reduction is small), with a reduced risk of caesarean section and little or no difference in operative vaginal birth. If women are offered the option of labour induction, it may be helpful for health professionals to provide information and resources about the absolute and relative risks of perinatal death at different gestational age time points. Recognising that women's assessments, circumstances, values and preferences may differ, ideally use of these resources would be tailored accordingly. If a woman chooses to wait for spontaneous labour onset, it may be prudent to have regular fetal monitoring, as longitudinal epidemiological studies suggest increased risk of perinatal death by increasing gestational age.

Implications for research.

The optimal timing of offering induction of labour to women at or beyond 37 weeks' gestation needs further investigation, as does further exploration of risk profiles of women and their values and preferences. While existing trials have not yet reported on childhood neurodevelopment, this is an important area for future research.

Feedback

Marowitz, 14 April 2011

Summary

Both my students and myself are unable to understand the following sentence in text for ‘Effects of the intervention':

"Women induced at 37 to 40 completed weeks were more likely to have a caesarean section with expectant management than those in the labour induction group (RR 0.58; 95% CI 0.34 to 0.99)."

Are there errors in the wording of this sentence?

[Comment submitted by Amy Marowitz, April 2011]

Reply

Thank you for your feedback. We have corrected the error.

Contributors

A Metin Gülmezoglu

Keulen et al, 1 August 2020

Summary

With great interest we have read the recently published updated review by Middleton et al on Induction of labour at or beyond 37 weeks (1). However, as authors of the included INDEX trial (2) we would like to comment on several points in this review.

1. Categorisation of groups

Timing of induction has been categorised in the intervention arm into three groups: induction at < 40 weeks, induction between 40 to 41 weeks and induction at > 41 weeks. With this categorisation 410 weeks is not included in one of the groups. In our trial, but also in the Wennerholm et al. trial (3) (a total of 4561 women), induction at 410 weeks or 411 weeks was compared with expectant management. We suggest to change the category of induction at > 41 weeks into ≥ 41 weeks.

2. Detection bias

In the risk of bias assessment paragraph of the Cochrane review is written: “Keulen 2019 and Wennerholm 2019 explicitly reported on the absence of blinding for outcome assessors (caregivers) and were thus both rated as high risk of bias.” Caregivers were aware of group assignments because of the nature of the intervention of the included trials. It is not possible to blind caregivers, therefore this kind of bias applies to all included trials (no blinding of patients or personnel). However, this does not concern detection bias. In our trial the outcome assessor was a statistician who was blinded for the allocation, as is described explicitly in our publication and trial protocol. (quote from the statistical paragraph in our article: ‘The statistician who performed the analyses was blinded to the allocation of the participants and performed the analysis according to a predefined analysis plan.’)

3. Reporting bias

In this section is written: “Keulen 2019; to be at unclear risk of reporting bias, largely due to insufficient information to assess selective reporting (i.e. no access to trial protocols and limited detail reported in manuscript methods).”

Our trial protocol is published (4) and we had a predefined analysis plan as we have reported in our article. Therefore we wonder what kind of information is missing.

4. Induction setting (start and waiting)

In Table 3 the induction setting is described. However, this is not correct for our induction group as induction took always place in obstetrician led care in the hospital (start and waiting) as is described as such in our article (quote 1: ‘Women allocated to induction were scheduled for the procedure at 41 weeks+0 days‐41 weeks+1 day’ and quote 2: ‘all women in the 41 week induction group received obstetrician led intrapartum secondary care’. We assumed it a matter of course that a scheduled induction procedure (start and waiting) was done in a hospital setting since that was the mainstream procedure at the time of inclusion.

5. Causes of death (stillbirths and livebirth deaths)

In table 5 it is reported that the causes of perinatal death are not described in our publication. However, we gave a full description of the cases in our paper:

(Quote) “Three perinatal deaths (stillbirths) occurred: one in the induction group and two in the expectant management group. There were no neonatal deaths. The stillbirth in the induction group was in a 30 year old multiparous woman who was randomised at 40 weeks+5 days and scheduled for induction at 41 weeks+1 day. She had reduced fetal movements at 40 weeks+6 days, and fetal death was diagnosed at consultation. She delivered a neonate weighing 3595 g (20th to 50th centiles). Investigations, including a postmortem examination, did not explain the stillbirth. In the expectant management group, stillbirth was diagnosed in a 36 year old nulliparous woman at 41 weeks+3 days, when she was admitted to hospital in labour. She delivered a neonate weighing 2945 g (5th to 10th centiles). Investigations, including placental examination, did not explain the stillbirth, and the parents declined a postmortem examination. The second stillbirth in the expectant management group was diagnosed in a 32 year old multiparous woman at 41 weeks+4 days during a regular consultation in secondary care for impending post‐term pregnancy. She delivered a neonate weighing 3715 g (20th to 50th centiles). No postmortem examination was performed, but the placenta showed signs of chorioamnionitis.”

Also, in the paragraph describing the primary outcome perinatal death, it was reported that Wennerholm et al. (2019) was the only trial reporting perinatal death by parity, though as is shown in the above copy‐paste of our article, we clarified the parity for the cases of perinatal mortality in the article.

6. General remarks

Finally, we have two general remarks:

In Table 4 (Rates of perinatal death by gestation) the last group is called > 42, while this should be > 41 weeks (or to be totally correct ≥ 41 weeks).
The rate of meconium aspiration syndrome of the Sahraoui et al. trial is not reported in the original publication but the incidence of meconium stained amniotic fluid. (quote from original article: ‘un liquide amniotique teinté ou méconial était plus fréquemment rentcontré dans le groupe “surveillance”(44%) que dans le group “Prépidil (25,3%) (p=0.013)’ ). Because this concerns relatively high numbers (33 versus 19) this may affect the RR (Analyis 1.9) and funnel plot (figure 8) of meconium aspiration syndrome. (5)

Since the Cochrane review is the source for many caregivers and guideline developers who rely on the judgement of the quality of the included studies, we hope for a rapid processing of our comments.

Yours sincerely, on behalf of the INDEX‐team

Judit Keulen (first author), Esteriek de Miranda (project leader), Joris van der Post (guarantor)

References:

Middleton P, Shepherd E, Morris J, Crowther CA, Gomersall JC. Induction of labour at or beyond 37 weeks' gestation. Cochrane Database Syst Rev. 2020;7:CD004945.
Keulen JK, Bruinsma A, Kortekaas JC, van Dillen J, Bossuyt PM, Oudijk MA, et al. Induction of labour at 41 weeks versus expectant management until 42 weeks (INDEX): multicentre, randomised non‐inferiority trial. BMJ. 2019;364:l344.
Wennerholm UB, Saltvedt S, Wessberg A, Alkmark M, Bergh C, Wendel SB, et al. Induction of labour at 41 weeks versus expectant management and induction of labour at 42 weeks (SWEdish Post‐term Induction Study, SWEPIS): multicentre, open label, randomised, superiority trial. BMJ. 2019;367:l6131.
Kortekaas JC, Bruinsma A, Keulen JK, van Dillen J, Oudijk MA, Zwart JJ, et al. Effects of induction of labour versus expectant management in women with impending post‐term pregnancies: the 41 week ‐ 42 week dilemma. BMC pregnancy and childbirth. 2014;14:350.
Keulen JKJ, Bruinsma A, Kortekaas JC, van Dillen J, van der Post JAM, de Miranda E. Timing induction of labour at 41 or 42 weeks? A closer look at time frames of comparison: A review. Midwifery. 2018;66:111‐8.

Reply

1. Categorisation of groups

Response:

Changed as requested, this has not impacted on the results.

2. Detection bias

Response:

Changed to low risk of bias (and results text changed accordingly).

3. Reporting bias

Our trial protocol is published (4) and we had a predefined analysis plan as we have reported in our article. Therefore we wonder what kind of information is missing.

Response:

Changed to low risk of bias (and results text changed accordingly); we note that your paper on women’s preferences has now been published.

4. Induction setting (start and waiting)

Response:

Changed to ‘all women in the 41 week induction group received obstetrician led intrapartum secondary care’.

5. Causes of death (stillbirths and livebirth deaths)

In table 5 it is reported that the causes of perinatal death are not described in our publication. However, we gave a full description of the cases in our paper:

Response:

Changed to: “The stillbirth in the induction group was in a 30 year old multiparous woman who was randomised at 40 weeks+5 days and scheduled for induction at 41 weeks+1 day. She had reduced fetal movements at 40 weeks+6 days, and fetal death was diagnosed at consultation. She delivered a neonate weighing 3595 g (20th to 50th centiles). Investigations, including a postmortem examination, did not explain the stillbirth.”

In the expectant management group, stillbirth was diagnosed in a 36 year old nulliparous woman at 41 weeks+3 days, when she was admitted to hospital in labour. She delivered a neonate weighing 2945 g (5th to 10th centiles). Investigations, including placental examination, did not explain the stillbirth, and the parents declined a postmortem examination. The second stillbirth in the expectant management group was diagnosed in a 32 year old multiparous woman at 41 weeks+4 days during a regular consultation in secondary care for impending post‐term pregnancy. She delivered a neonate weighing 3715 g (20th to 50th centiles). No postmortem examination was performed, but the placenta showed signs of chorioamnionitis.”

Regarding the feedback paragraph about describing the primary outcome perinatal death, we have added Keulen text on parity to this paragraph.

General remarks

Finally, we have two general remarks:

In Table 4 (Rates of perinatal death by gestation) the last group is called > 42, while this should be > 41 weeks (or to be totally correct ≥ 41 weeks).

Response:

Changed to ≥ 41 weeks

The rate of meconium aspiration syndrome of the Sahraoui et al. trial is not reported in the original publication but the incidence of meconium stained amniotic fluid. (quote from original article: ‘un liquide amniotique teinté ou méconial était plus fréquemment rentcontré dans le groupe “surveillance”(44%) que dans le group “Prépidil (25,3%) (p=0.013)’ ). Because this concerns relatively high numbers (33 versus 19) this may affect the RR (Analyis 1.9) and funnel plot (figure 8) of meconium aspiration syndrome. (5)

Response:

While we acknowledge that the definition has some ambiguity, we have retained the data from Sahraoui. Though the magnitude differs somewhat, the overall finding remains similar.

Contributors

Philippa Middleton, Emily Shepherd, Jonathan Morris, Caroline Crowther, Judith Gomersall, 7 August 2020.

What's new

Date	Event	Description
24 August 2020	Amended	Review amended in relation to feedback.
24 August 2020	Feedback has been incorporated	Added comments from Judit Keulen, 1 August 2020 and responses from the authors dated 7 August 2020 ‐ see Feedback 2

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History

Protocol first published: Issue 4, 2004 Review first published: Issue 4, 2006

Date	Event	Description
27 March 2020	New citation required and conclusions have changed	Operative vaginal birth now shows little or no difference with a policy of induction (moderate‐certainty evidence). The four new trials have nearly doubled the number of participants to over 21,000, with a concomitant increase in GRADE certainty for perinatal mortality and neonatal intensive care unit admission from moderate to high.
17 July 2019	New search has been performed	Search updated. Four new included trials added, two new ongoing trials added.
28 December 2017	New search has been performed	Search updated and eight additional trials included (Brane 2014; Cohn 1992; Keulen 2019; Martin 1978; Miller 2015; Sande 1983; Tylleskar 1979; Walker 2016). We have updated the methods in line with the standard methods used by Cochrane Pregnancy and Childbirth and we now use GRADE to assess the quality of the body of evidence. For this update, the overall conclusions have not changed. However, there is moderate certainty evidence to suggest that induction was associated with fewer stillbirths and fewer babies with low Apgar scores.
9 October 2017	New citation required but conclusions have not changed	Conclusions not changed.
31 March 2012	New search has been performed	Search updated ‐ no new trials identified. Trial reports that were previously awaiting classification have now been incorporated into the review. We have added three new included trials (Heimstad 2007; Nielsen 2005; Sahraoui 2005), three new excluded trials (Hernandez‐Castro 2008; Imsuwan 1999; Nicholson 2008) and one ongoing trial (Rijnders 2007). This updated review is now comprised of 22 included studies (reporting on 9383 women); 64 excluded studies and one ongoing study. Results are now presented as 37‐39 weeks; 39‐40 weeks; < 41 weeks, 41 weeks and > 41 weeks. A new author joined the team to help prepare this update.
31 March 2012	New citation required and conclusions have changed	Whilst the overall conclusions have not changed, there is now evidence to show that induction of labour at or beyond term is associated with a lower rate of caesarean section.
6 July 2011	Amended	Error corrected in response to feedback from Amy Marowitz (Feedback).
6 July 2011	Feedback has been incorporated	Feedback from Amy Marowitz added.
14 July 2009	Amended	Search updated. Eight reports of five trials added to Studies awaiting classification (Heimstad 2007a; Hernandez‐Castro 2008a; Imsuwan 1999a; Nicholson 2008a; Rijnders 2007a).
3 September 2008	Amended	Converted to new review format.
28 February 2007	Amended	The Implications for research section has been amended to include the uncertainty about timing of labour induction beyond term, which was unintentionally left out during the revision process.
21 August 2006	New citation required but conclusions have not changed	This version has been re‐written, including a new protocol which now limits the scope to labour induction
30 June 2006	New search has been performed	The previous version of this review included studies up to 1997 and included 21 labour induction trials (Gülmezoglu 2006). This version has been re‐written, including a new protocol which now limits the scope to labour induction, and includes 19 trials. Thirteen of the 21 trials included in the previous version are included in this version. The remaining eight trials were excluded because of alternate allocation (Cardozo 1986; Heden 1991; Katz 1983), a high proportion of postrandomization exclusion (greater than 30% in Martin 1978a and greater than 24% in Tylleskar 1979a), cervical ripening with breast stimulation (Elliott 1984; Kadar 1990), and analysis by intervention received (i.e. groups switched, Sande 1983a). Six trials published since the publication of the previous version have been included in this update (Chakravarti 2000; Chanrachkul 2003; Gelisen 2005; James 2001; Ocon 1997; Roach 1997).

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Acknowledgements

We acknowledge the support from Cochrane Pregnancy and Childbirth editorial team in Liverpool and the Australian and New Zealand Satellite of Cochrane Pregnancy and Childbirth.

We thank Therese Dowswell from Cochrane Pregnancy and Childbirth who provided support for the 2018 update. Therese assisted with data extraction, and the production of 'Summary of findings' tables.

We would like to acknowledge the contribution of Machiko Suganuma who assisted with data extraction for the 2018 update.

We would like to acknowledge the contribution of A Metin Gulmezoglu who initiated, led and assisted in the review preparation until 2016 and Emer Van Ryswyk for her contribution to a previous version of this review (Gülmezoglu 2012).

As part of the pre‐publication editorial process, this review has been commented on by three peers (an editor and two referees who are external to the editorial team), a member of our international panel of consumers and our Group's Statistical Adviser. The authors are grateful to the following peer reviewers for their time and comments: Jim Thornton, Professor of Obstetrics and Gynaecology, University of Nottingham, UK; Rory Windrom, Department of Obstetrics and Gynaecology, University of Toronto, Canada.

This project was supported by the National Institute for Health Research (NIHR), via Cochrane programme grant funding, and Cochrane Infrastructure funding to Cochrane Pregnancy and Childbirth. The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the Systematic Reviews Programme, NIHR, National Health Service or the Department of Health.

This review is supported by funding from the UNDP‐UNFPA‐UNICEF‐WHO‐World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP), Department of Sexual and Reproductive Health and Research, World Health Organization to Cochrane Pregnancy and Childbirth (University of Liverpool). HRP supports and co‐ordinates research on a global scale, synthesises research through systematic reviews of literature, builds research capacity in low‐ and middle‐income countries and develops dissemination tools to make efficient use of ever‐increasing research information. In addition to its co‐sponsors, the International Planned Parenthood Federation (IPPF) and UNAIDS are both members of HRP’s governing body.

Appendices

Appendix 1. Search methods used for ICTRP and ClinicalTrials.gov

ICTRP

Each line was run separately

induction AND expectant

induction AND wait(ing)

post‐term

postterm

postdate(s)

post‐date(s)

term AND pregnancy and expectant

ClinicalTrials.gov

Each combination of terms was run separately.

Advanced search ‐ Intervention studies

pregnancy, prolonged AND (expectant OR wait OR waiting OR monitor)

post‐term pregnancy AND (expectant OR wait OR waiting OR monitor)

expectant AND labor

postterm OR post‐term

postdates OR post‐dates

Data and analyses

Comparison 1. Labour induction versus expectant management (all trials).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1.1 Perinatal death	22	18795	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.15, 0.64]
1.2 Stillbirth	22	18795	Risk Ratio (M‐H, Fixed, 95% CI)	0.30 [0.12, 0.75]
1.3 Neonatal death	21	18611	Risk Ratio (M‐H, Fixed, 95% CI)	0.39 [0.13, 1.14]
1.4 Birth asphyxia	4	1456	Risk Ratio (M‐H, Fixed, 95% CI)	1.66 [0.61, 4.55]
1.5 Admission to neonatal intensive care unit	17	17826	Risk Ratio (M‐H, Fixed, 95% CI)	0.88 [0.80, 0.96]
1.6 Neonatal convulsions	5	13216	Risk Ratio (M‐H, Random, 95% CI)	1.01 [0.15, 6.67]
1.7 Neonatal encephalopathy (HIE)	2	8851	Risk Ratio (M‐H, Fixed, 95% CI)	0.69 [0.37, 1.31]
1.8 Use of anticonvulsants	1	349	Risk Ratio (M‐H, Fixed, 95% CI)	0.34 [0.01, 8.17]
1.9 Meconium aspiration syndrome	13	16622	Risk Ratio (M‐H, Fixed, 95% CI)	0.75 [0.62, 0.92]
1.10 Pneumonia	2	8851	Risk Ratio (M‐H, Fixed, 95% CI)	0.54 [0.27, 1.06]
1.11 Apgar score less than 7 at 5 minutes	20	18345	Risk Ratio (M‐H, Fixed, 95% CI)	0.73 [0.56, 0.96]
1.12 Birthweight (g)	18	8817	Mean Difference (IV, Fixed, 95% CI)	‐59.38 [‐77.03, ‐41.73]
1.13 Birthweight > 4000 g	8	5593	Risk Ratio (M‐H, Random, 95% CI)	0.72 [0.54, 0.96]
1.14 Neonatal (birth) trauma	5	13106	Risk Ratio (M‐H, Fixed, 95% CI)	0.97 [0.63, 1.49]
1.15 Caesarean section	31	21030	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.85, 0.95]
1.16 Operative vaginal birth (forceps or ventouse)	22	18584	Risk Ratio (M‐H, Fixed, 95% CI)	1.03 [0.96, 1.10]
1.17 Analgesia used	12		Risk Ratio (M‐H, Random, 95% CI)	Subtotals only
1.17.1 Epidural/regional	8	4579	Risk Ratio (M‐H, Random, 95% CI)	1.09 [0.99, 1.20]
1.17.2 Other	4	2352	Risk Ratio (M‐H, Random, 95% CI)	1.11 [1.05, 1.18]
1.18 Perineal trauma	7		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
1.18.1 Severe perineal tear	5	11589	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.85, 1.26]
1.18.2 Episiotomy	2	1747	Risk Ratio (M‐H, Fixed, 95% CI)	0.96 [0.84, 1.11]
1.18.3 Obstetrical anal sphincter injuries	2	1698	Risk Ratio (M‐H, Fixed, 95% CI)	0.81 [0.51, 1.31]
1.19 Prolonged labour	4		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
1.19.1 First stage	2	648	Risk Ratio (M‐H, Fixed, 95% CI)	0.76 [0.49, 1.20]
1.19.2 Second stage	1	508	Risk Ratio (M‐H, Fixed, 95% CI)	0.67 [0.36, 1.22]
1.19.3 Third stage	1	249	Risk Ratio (M‐H, Fixed, 95% CI)	3.02 [0.12, 73.52]
1.19.4 No definition	1	112	Risk Ratio (M‐H, Fixed, 95% CI)	0.35 [0.01, 8.30]
1.20 Postpartum haemorrhage	9	12609	Risk Ratio (M‐H, Fixed, 95% CI)	1.02 [0.91, 1.15]
1.21 Breastfeeding	2	7487	Risk Ratio (M‐H, Fixed, 95% CI)	1.00 [0.96, 1.04]
1.22 Maternal satisfaction	3		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
1.22.1 Hoping to be randomised to the same trial arm as they had been in this study	1	496	Risk Ratio (M‐H, Fixed, 95% CI)	1.93 [1.62, 2.30]
1.22.2 Preferred/satisfied with their allocation	2	493	Risk Ratio (M‐H, Fixed, 95% CI)	0.99 [0.88, 1.13]
1.22.3 Satisfaction with pregnancy outcome	1	308	Risk Ratio (M‐H, Fixed, 95% CI)	0.92 [0.80, 1.06]
1.23 Maternal satisfaction	1	619	Mean Difference (IV, Fixed, 95% CI)	0.07 [‐0.02, 0.16]
1.24 Length of maternal hospital stay (days)	7	4120	Mean Difference (IV, Random, 95% CI)	‐0.19 [‐0.56, 0.18]
1.25 Length of maternal (postnatal) stay (categories)	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
1.25.1 < 2 days	1	6096	Risk Ratio (M‐H, Fixed, 95% CI)	1.01 [0.87, 1.17]
1.25.2 2 days	1	6096	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [1.01, 1.08]
1.25.3 3 days	1	6096	Risk Ratio (M‐H, Fixed, 95% CI)	0.88 [0.77, 0.99]
1.25.4 4 days	1	6096	Risk Ratio (M‐H, Fixed, 95% CI)	0.78 [0.62, 0.97]
1.25.5 > 4 days	1	6096	Risk Ratio (M‐H, Fixed, 95% CI)	0.94 [0.48, 1.82]
1.26 Length of neonatal hospital stay (days)	1	302	Mean Difference (IV, Fixed, 95% CI)	‐0.30 [‐0.61, 0.01]
1.27 Length of neonatal (postnatal) stay (categories)	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
1.27.1 ≤ 2 days	1	6091	Risk Ratio (M‐H, Fixed, 95% CI)	1.05 [1.02, 1.08]
1.27.2 ≥ 3 days	1	6091	Risk Ratio (M‐H, Fixed, 95% CI)	0.86 [0.79, 0.94]
1.28 Length of labour (hours)	12	4025	Mean Difference (IV, Random, 95% CI)	‐1.08 [‐1.67, ‐0.50]

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Comparison 2. Labour induction versus expectant management (subgroup analysis by gestational age at induction).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2.1 Perinatal death	22	18795	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.15, 0.64]
2.1.1 < 40 weeks	4	7126	Risk Ratio (M‐H, Fixed, 95% CI)	0.50 [0.13, 2.01]
2.1.2 40 to 41 weeks	3	760	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.01, 7.45]
2.1.3 ≥ 41 weeks	15	10909	Risk Ratio (M‐H, Fixed, 95% CI)	0.26 [0.11, 0.64]
2.2 Stillbirth	22	18795	Risk Ratio (M‐H, Fixed, 95% CI)	0.30 [0.12, 0.75]
2.2.1 < 40 weeks	4	7126	Risk Ratio (M‐H, Fixed, 95% CI)	0.51 [0.09, 2.76]
2.2.2 40 to 41 weeks	3	760	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.01, 7.45]
2.2.3 ≥ 41 weeks	15	10909	Risk Ratio (M‐H, Fixed, 95% CI)	0.24 [0.08, 0.78]
2.3 Admission to neonatal intensive care unit	17	17826	Risk Ratio (M‐H, Fixed, 95% CI)	0.88 [0.80, 0.96]
2.3.1 < 40 weeks	5	7409	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.79, 1.02]
2.3.2 40 to 41 weeks	3	527	Risk Ratio (M‐H, Fixed, 95% CI)	1.68 [0.53, 5.29]
2.3.3 ≥ 41 weeks	9	9890	Risk Ratio (M‐H, Fixed, 95% CI)	0.84 [0.74, 0.96]
2.4 Caesarean section	31	21030	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.85, 0.95]
2.4.1 < 40 weeks	8	8537	Risk Ratio (M‐H, Fixed, 95% CI)	0.87 [0.80, 0.95]
2.4.2 40 to 41 weeks	6	1189	Risk Ratio (M‐H, Fixed, 95% CI)	1.12 [0.88, 1.43]
2.4.3 ≥ 41 weeks	17	11304	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.83, 0.97]
2.5 Operative vaginal birth (forceps or ventouse)	22	18584	Risk Ratio (M‐H, Fixed, 95% CI)	1.03 [0.96, 1.10]
2.5.1 < 40 weeks	7	8376	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.93, 1.16]
2.5.2 40 to 41 weeks	4	707	Risk Ratio (M‐H, Fixed, 95% CI)	1.64 [0.82, 3.29]
2.5.3 ≥ 41 weeks	11	9501	Risk Ratio (M‐H, Fixed, 95% CI)	1.01 [0.92, 1.11]
2.6 Perineal trauma	5	11589	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.85, 1.26]
2.6.1 < 40 weeks	2	6714	Risk Ratio (M‐H, Fixed, 95% CI)	1.18 [0.90, 1.55]
2.6.2 40 to 41 weeks	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	Not estimable
2.6.3 ≥ 41 weeks	3	4875	Risk Ratio (M‐H, Fixed, 95% CI)	0.89 [0.66, 1.19]

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Comparison 3. Labour induction versus expectant management (subgroup analysis by parity).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
3.1 Perinatal death	22	18795	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.15, 0.64]
3.1.1 Nulliparous	3	8229	Risk Ratio (M‐H, Fixed, 95% CI)	0.26 [0.06, 1.05]
3.1.2 Mixed (primi‐ and multiparous)	18	10470	Risk Ratio (M‐H, Fixed, 95% CI)	0.33 [0.14, 0.78]
3.1.3 Not stated	2	96	Risk Ratio (M‐H, Fixed, 95% CI)	Not estimable
3.2 Stillbirth	22	18795	Risk Ratio (M‐H, Fixed, 95% CI)	0.30 [0.12, 0.74]
3.2.1 Nulliparous	3	8229	Risk Ratio (M‐H, Fixed, 95% CI)	0.23 [0.04, 1.35]
3.2.2 Mixed (primi‐ and multiparous)	18	10470	Risk Ratio (M‐H, Fixed, 95% CI)	0.33 [0.12, 0.97]
3.2.3 Not stated	2	96	Risk Ratio (M‐H, Fixed, 95% CI)	Not estimable
3.3 Admission to neonatal intensive care unit	17	17826	Risk Ratio (M‐H, Fixed, 95% CI)	0.88 [0.80, 0.96]
3.3.1 Nulliparous	5	7312	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.79, 1.03]
3.3.2 Mixed (primi‐ and multiparous)	10	10200	Risk Ratio (M‐H, Fixed, 95% CI)	0.83 [0.73, 0.95]
3.3.3 Not stated	2	314	Risk Ratio (M‐H, Fixed, 95% CI)	1.20 [0.70, 2.06]
3.4 Caesarean section	31	21030	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.85, 0.95]
3.4.1 Nulliparous	6	7543	Risk Ratio (M‐H, Fixed, 95% CI)	0.89 [0.81, 0.97]
3.4.2 Mixed (primi‐ and multiparous)	20	12877	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.83, 0.97]
3.4.3 Not stated	5	610	Risk Ratio (M‐H, Fixed, 95% CI)	1.12 [0.81, 1.56]
3.5 Operative vaginal birth (forceps or ventouse)	22	18584	Risk Ratio (M‐H, Fixed, 95% CI)	1.03 [0.96, 1.10]
3.5.1 Nulliparous	4	7151	Risk Ratio (M‐H, Fixed, 95% CI)	0.96 [0.84, 1.09]
3.5.2 Mixed (primi‐ and multiparous)	15	11224	Risk Ratio (M‐H, Fixed, 95% CI)	1.06 [0.97, 1.15]
3.5.3 Not stated	3	209	Risk Ratio (M‐H, Fixed, 95% CI)	1.09 [0.58, 2.06]
3.6 Perineal trauma (severe perineal tear)	5	11589	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.85, 1.26]
3.6.1 Nulliparous	2	6714	Risk Ratio (M‐H, Fixed, 95% CI)	1.18 [0.90, 1.55]
3.6.2 Mixed (primi‐ and multiparous)	3	4875	Risk Ratio (M‐H, Fixed, 95% CI)	0.89 [0.66, 1.19]

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Comparison 4. Labour induction versus expectant management (subgroup analysis by status of cervix).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4.1 Perinatal death	22	18795	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.15, 0.64]
4.1.1 Favourable cervix	3	760	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.01, 7.45]
4.1.2 Unfavourable cervix	7	4938	Risk Ratio (M‐H, Fixed, 95% CI)	0.29 [0.07, 1.17]
4.1.3 Unknown/mixed state of cervix	12	13097	Risk Ratio (M‐H, Fixed, 95% CI)	0.32 [0.13, 0.77]
4.2 Stillbirth	22	18795	Risk Ratio (M‐H, Fixed, 95% CI)	0.30 [0.12, 0.75]
4.2.1 Favourable cervix	3	760	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.01, 7.45]
4.2.2 Unfavourable cervix	7	4938	Risk Ratio (M‐H, Fixed, 95% CI)	0.27 [0.05, 1.66]
4.2.3 Unknown/mixed state of cervix	12	13097	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.10, 0.95]
4.3 Admission to neonatal intensive care unit	17	17826	Risk Ratio (M‐H, Fixed, 95% CI)	0.88 [0.80, 0.96]
4.3.1 Favourable cervix	2	475	Risk Ratio (M‐H, Fixed, 95% CI)	3.02 [0.12, 73.52]
4.3.2 Unfavourable cervix	6	4529	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.77, 1.05]
4.3.3 Unknown/mixed state of cervix	9	12822	Risk Ratio (M‐H, Fixed, 95% CI)	0.86 [0.77, 0.97]
4.4 Caesarean section	31	21030	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.85, 0.95]
4.4.1 Favourable cervix	4	906	Risk Ratio (M‐H, Fixed, 95% CI)	1.12 [0.76, 1.65]
4.4.2 Unfavourable cervix	10	5361	Risk Ratio (M‐H, Fixed, 95% CI)	0.92 [0.83, 1.01]
4.4.3 Unknown/mixed state of cervix	17	14763	Risk Ratio (M‐H, Fixed, 95% CI)	0.88 [0.82, 0.95]
4.5 Operative vaginal birth (forceps or ventouse)	22	18584	Risk Ratio (M‐H, Fixed, 95% CI)	1.03 [0.96, 1.10]
4.5.1 Favourable cervix	3	655	Risk Ratio (M‐H, Fixed, 95% CI)	0.87 [0.42, 1.82]
4.5.2 Unfavourable cervix	5	3799	Risk Ratio (M‐H, Fixed, 95% CI)	1.06 [0.95, 1.18]
4.5.3 Unknown/mixed state of cervix	14	14130	Risk Ratio (M‐H, Fixed, 95% CI)	1.01 [0.92, 1.11]
4.6 Perineal trauma	5	11589	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.85, 1.26]
4.6.1 Unknown/mixed state of cervix	5	11589	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.85, 1.26]

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4.6 — Comparison 4: Labour induction versus expectant management (subgroup analysis by status of cervix), Outcome 6: Perineal trauma

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Augensen 1987.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 409 Setting: Bergen, Norway Study date: 1981‐84 (no further details) Inclusion criteria Healthy women Normal pregnancy Singleton Cephalic presentation Duration of pregnancy 290‐297 days from the first day of the LMP Reliable dates GA for intervention: 41+ weeks (290‐297 days) Primiparous (44%) and multiparous Exclusion criteria Use of contraceptive pills during the 2 months before the LMP State of cervix: mixed (about 35% in each group had unripe cervix)
Interventions	Induction group (n = 214): immediate induction with oxytocin (5 IU increased in a stepwise manner). GA at intervention 41+ weeks (290‐297 days) versus EM group (n = 195): NST every 3‐4 days, IOL after 7 days
Outcomes	Mother: caesarean section; assisted vaginal birth; length of labour; length of hospital stay Baby: perinatal death; birthweight; neonatal jaundice; meconium‐stained amniotic fluid; NICU admission
Notes	Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	List of random numbers
Allocation concealment (selection bias)	Unclear risk	Allocation concealment was unclear given that it was not undertaken by a staff member or team member clearly uninvolved in the trial. It was reported that the midwife undertook allocation using a random number list, and this list was inaccessible to the participating physicians.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	4/214 in the IOL group went into labour before IOL but data for these women have been included in the IOL group for analyses. No apparent losses to follow‐up or exclusions.
Selective reporting (reporting bias)	High risk	No outcomes were prespecified in the methods; some outcomes reported incompletely in text, e.g. "There was no significant difference between the groups in the use of analgesia, sedatives, and epidural anaesthesia".
Other bias	Low risk	Appears to be free of other bias.

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Baev 2017.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 156 Setting: Tertiary referral hospital, Moscow, Russia Study date: study conducted January 2014‐15 Inclusion criteria Between 18 and 45 years Singleton live pregnancies Cephalic presentation GA: at least 40⁴ weeks' gestation Unripe cervix at the moment of enrolment (Bishop score < 8) Intact membranes No contraindication for vaginal birth or for labour induction with mifepristone, prostaglandin or oxytocin Informed consent Exclusion criteria Myoma/uterine anomaly Parity > 3 Severe hypertension/pre‐eclampsia Prior caesarean Diabetes, impaired renal, adrenal, or hepatic function, fetal malformations, breech presentation Estimated fetal weight (> 4500 or < 2500 g), any concerns about the well‐being of the fetus, any medical indication for scheduled caesarean birth State of cervix: unfavourable at trial entry (Bishop score < 8 at enrolment)
Interventions	Induction group (n = 78): mifepristone for cervical ripening and IOL (200 mg orally at the time of enrolment and, if applicable, second dose after 24 hours). If after 72 hours the Bishop score had not changed, induction was considered 'failed'; if the Bishop score was 6‐7, dinoprostone (PGE2, gel, into the cervical canal) (0.5 mg initially, followed by a second and third dose at 6 and 12 hours if required). When Bishop score was ≥ 8, women were transferred to the labour ward for AROM. If after 4 hours there were no uterine contractions, IV oxytocin was given (starting at an incremental dose of 3 mU/minute) versus EM group (n = 78): routine appointments except examination of Bishop score after 24 and 48 hours; evaluation for maternal and fetal well‐being (including CTG). IOL at 42 weeks' gestation if birth had not yet occurred.
Outcomes	Mother: caesarean section; assisted vaginal birth (vacuum extraction, forceps delivery); analgesia used (regional analgesia); postpartum haemorrhage; perineal trauma (episiotomy, perineal laceration 1‐2 degree); prolonged labour (protracted active phase); length of labour Baby: birthweight; Apgar score (less than or equal to 7 at 5 minutes); NICU admission
Notes	Funding: none declared Declarations of interest: none declared
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated list of random numbers organised into permuted blocks of 4
Allocation concealment (selection bias)	Low risk	Sequentially numbered, opaque envelopes sealed by independent staff member
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding of participants and personnel was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	Trialists reported that 74/78 (95%) of intervention group women allocated were included in analyses (1 woman lost to follow‐up, intervention discontinued in 2 women due to PROM, 1 woman dropped out due to skin rash reaction to drug). 75/78 (96%) of control group women analysed (3 women lost to follow‐up).
Selective reporting (reporting bias)	Unclear risk	Could not determine without access to protocol. Perinatal death, stillbirth or neonatal death not reported (and not specified in list of exclusions)
Other bias	Low risk	Appeared to be free of other bias, however, unclear why intrapartum characteristics were available only for 70 women in each group

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Bergsjo 1989.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 188 Setting: Wuhan, Hubei province, China Study date: study conducted 1 July 1982 to January 1985 (enrolment ended early 1984) Inclusion criteria All parities Not in labour Intact membranes Normal pregnancy No significant risk factors GA for intervention: 42⁺ completed weeks (294⁺ days) Exclusion criteria No additional criteria State of cervix: not mentioned
Interventions	Induction group (n = 94): stripping of membranes followed by oxytocin infusion and AROM if cervix sufficiently dilated. GA for intervention: 42 completed weeks (294 days) versus EM group (n = 94): no intervention for 1 week, IOL at 43 weeks.
Outcomes	Mother: operative vaginal birth; duration of labour; caesarean section; breastfeeding (timing of recording of this outcome in relation to birth or discharge time was not specified) Baby: perinatal death; meconium aspiration syndrome
Notes	Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	List of random numbers
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	8/94 in IOL group went into labour before IOL but were kept in the allocated group. No apparent losses to follow‐up or exclusions
Selective reporting (reporting bias)	High risk	Most prespecified outcomes were reported; however, limited information was provided for some outcomes (e.g. combined maternal complications) and neonatal outcomes, e.g. "Maternal complications, including protracted labour, cervical edema, cervical laceration, postpartum hemorrhage and unspecified postpartum morbidity accounted to about 15% in both groups, with no significant differences;" and "About 90 mothers in each group were breastfeeding."
Other bias	Low risk	Appeared to be free of other bias

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Brane 2014.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 138 Setting: Stockholm, Sweden Study conducted: women recruited June 2007 to May 2012 Inclusion criteria Nulliparous low‐risk women Normal pregnancies With contractions Singleton fetus with cephalic presentation GA: between 37⁺⁰ and 41⁺⁶ confirmed by ultrasound < 20 weeks Cervical dilation < 4 cm and intact membranes Able to speak, read and understand Swedish Exclusion criteria Not stated State of cervix: Bishop score at presentation ranged from 1‐8 in induction group and 2‐9 in EM group.
Interventions	Induction group (n = 71): 5 hours after medication to promote 'therapeutic rest' IOL performed, with method dependent on state of cervix: intravaginal PGE2 or transcervical catheter +/‐ AROM if cervical dilation permitted; followed by IV oxytocin (augmented every 20‐30 minutes) if no progress after AROM versus EM group (n = 67): spontaneous labour awaited as long as possible; IOL if women wanted, or if the obstetrician/midwife considered suitable
Outcomes	Mother: mode of birth; experience of birth; duration of labour; labour analgesia; oxytocin for augmentation; birth presentation; postpartum haemorrhage; sphincter tears Baby: Apgar score < 7 at 5 minutes; cord artery metabolic acidosis; birthweight; head circumference; admission to NICU
Notes	Women in both groups given medication to promote 'therapeutic rest' (1 g paracetamol, 10 mg zolpidem, 10 mg morphine). During active phase of labour (cervical dilation ≥ 4 cm or ROM) women monitored according to local protocol; slow progress (arrest of dilation for 2‐3 hours) was treated with AROM or oxytocin Funding: Karolinska Institute Foundations and Funds Declaration of interests: The authors reported no conflicts of interest.
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"The randomization was performed in blocks of 5–10 in each group." Method of sequence generation not reported
Allocation concealment (selection bias)	Unclear risk	"A sealed envelope containing coded protocols for the respective groups… was opened by the midwife." No further detail provided
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Some attrition and missing data, particularly for the women’s views questionnaire. Most of the sample were included in the analyses for the primary outcome (65/71, and 64/67 in main analysis for mode of birth). The reasons for missing data for some clinical outcomes were not reported.
Selective reporting (reporting bias)	Unclear risk	No access to trial protocol to confidently assess selective reporting. Perinatal death not reported
Other bias	Low risk	Appeared to be free of other bias

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Breart 1982.

*Study characteristics*
Methods	RCT (1:2 randomisation)
Participants	Number of women randomised: 716 Setting: Paris, France Study conducted: not reported Inclusion criteria: GA: 37‐39 weeks (259‐273 days) Exclusion criteria: high risk, contraindication for IOL State of cervix: not mentioned Parity: mixed (60% nulliparous)
Interventions	Induction group (n = 235): oxytocin and AROM at GA 37‐39 weeks versus EM group (n = 481): FHR checking and amnioscopy every 2‐3 days
Outcomes	Mother: duration of labour; mode of birth Baby: morbidity (Apgar scores, resuscitation)
Notes	Funding: not reported Declaration of interests: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not reported.
Allocation concealment (selection bias)	Unclear risk	It was reported that a closed envelope system was used for allocation concealment, although no further detail was available.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	202/235 in the induction group and 173/481 in the expectant group followed the trial protocol; trial results were reported for all 716 women and their babies.
Selective reporting (reporting bias)	Unclear risk	No access to trial protocol to confidently assess selective reporting. Perinatal death was not reported.
Other bias	Low risk	Appeared to be free of other bias

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Chakravarti 2000.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 231 Setting: Calcutta, India Study date: not reported Inclusion criteria Primips Low risk Uncomplicated pregnancy Confirmed dates GA: reported as "before 41 completed weeks" State of cervix: not mentioned
Interventions	Induction group (n = 117): IOL, no details of the method are available. versus EM group (n = 114 randomised): daily fetal movement counts, biophysical profile and ultrasound; IOL after 1 week.
Outcomes	Only caesarean section rates were adequately reported in the abstract.
Notes	Reported as conference abstract. Only data for caesarean included in meta‐analysis. Funding: not reported Declaration of interests: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not reported.
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Appeared that blinding was not feasible
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient information to determine
Selective reporting (reporting bias)	Unclear risk	No outcomes were prespecified in the methods (conference abstract). Insufficient information to determine
Other bias	Unclear risk	Unable to identify other bias based on the abstract

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Chanrachkul 2003.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 249 Setting: Bangkok, Thailand Study date: study conducted October 1998 to May 2000 Inclusion criteria Low risk No obstetric or medical complication GA: 280 to 287 days screened for eligibility; 41³ weeks (290 days at enrolment and induction) ~70% women nulliparous Exclusion criteria No additional criteria State of cervix: favourable (Bishop score 6 or more)
Interventions	Induction group (n = 124): AROM + oxytocin (if uterine contractions inadequate after 2 hours); versus EM group (n = 125): spontaneous labour awaited unless 1) non‐reactive NST or 2) amniotic fluid index < 5 cm or 3) medical or obstetric indication for birth or 4) reaching 44 completed weeks.
Outcomes	Mother: prolonged labour; modes of birth and their indications; death; postpartum haemorrhage Baby: perinatal death, birthweight; birth asphyxia, NICU admission, birthweight > 4000 g; Apgar < 7 at 5 minutes
Notes	Funding: Ramathibodi Hospital Research Grant 2/2542 Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation was carried out using computer‐generated numbers.
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	1 woman (in IOL group) excluded after randomisation because of misclassification (breech presentation). No apparent losses to follow‐up
Selective reporting (reporting bias)	Unclear risk	While prespecified outcomes (in the methods) were reported, no access to trial protocol to further assess selective reporting.
Other bias	Low risk	Appeared to be free of other bias

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Cohn 1992.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 248 Setting: Hong Kong, China Study date: not mentioned but abstract published in 1992 Inclusion criteria GA: "on reaching 42 weeks' gestation" No indication for immediate delivery Exclusion criteria Not described State of cervix: Not reported
Interventions	Induction group (n = not reported): induction versus EM group (n = not reported): women were seen twice weekly.
Outcomes	Mother: length of stay in hospital; analgesia; caesarean birth; meconium‐stained liquor Baby: neonatal admission for meconium aspiration; birthweight; Apgar scores; umbilical cord vein pH
Notes	Abstract only. No data included in meta‐analyses Funding: not reported Declaration of interests: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	" A prospective randomised study". The method of sequence generation was not reported.
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	No information on losses to follow‐up or exclusions
Selective reporting (reporting bias)	Unclear risk	Abstract only
Other bias	Unclear risk	Abstract only. Baseline characteristics were not described.

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Cole 1975.

*Study characteristics*
Methods	Randomly allocated, no further details available
Participants	Number of women randomised: 228 Setting: Glasgow, Scotland Study date: not reported Inclusion criteria Primigravidae aged 18‐30 years 1‐3 parity, aged 18‐35 years who had previous pregnancies without any obstetric abnormality Certain date of LMP Regular menstrual cycle Early examination which had shown the uterine size to be consistent with the period of amenorrhoea GA: 39‐40 weeks State of cervix: not reported
Interventions	Induction group (n = 111): IOL with AROM + oxytocin versus EM group (n = 117): no intervention until 41 weeks, thereafter IOL
Outcomes	Mother: length of labour; mode of birth (including operative versus non operative); analgesia requirements; postpartum blood loss Baby: perinatal deaths; meconium staining; Apgar scores; birthweight; neonatal jaundice
Notes	Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not reported.
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	7/118 and 2/119 in the intervention and control groups excluded after randomisation because of misclassification as low risk
Selective reporting (reporting bias)	Unclear risk	No outcomes were prespecified in the methods; no access to trial protocol to further assess selective reporting
Other bias	Low risk	Appeared to be free of other bias

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Dyson 1987.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 302 Setting: Kaiser Permanente Medical Care Hospital in California, USA Study date: study conducted 11 January 1983 to 3 December 1985 Inclusion criteria Well‐established GA of at least 287 days GA at intervention: at least 41 completed weeks (287 days) Parity: ~70% nulliparous Exclusion criteria Non‐reactive NST result Variable decelerations on NST Oligohydramnios Any risk factors known to increase perinatal death and morbidity rates (such as chronic hypertension, pre‐eclampsia, diabetes mellitus, growth restriction and previous stillbirth) Any risk factors known to increase the risk of induction, such as multiple gestation and polyhydramnios Any risk factors known to markedly increase the caesarean section rate, such as breech presentation and previous caesarean section Cervical score of > 6 State of cervix: unfavourable (Bishop score < 6)
Interventions	Induction group (n = 152): PE2 gel (initially 3 mg but later reduced to 0.5 mg). If no labour in 24 hours, repeat PE2 and oxytocin if needed versus EM group (n = 150): NST twice weekly, pelvic examination and amniotic fluid determination weekly between 41‐42 weeks and twice weekly afterwards
Outcomes	Mother: length of hospital stay; caesarean section; length of labour Baby: perinatal death; 1 minute Apgar score < 7; 5 minute Apgar score < 7; meconium‐stained amniotic fluid; meconium aspiration syndrome; post‐maturity syndrome; fetal distress; birthweight; birthweight > 4000 g; infant hospital stay length
Notes	Funding: Community Service Program of Kaiser Foundation Hospitals Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	A table of random numbers was used.
Allocation concealment (selection bias)	Unclear risk	The authors reported " using a series of consecutively numbered, sealed envelopes..." for allocation concealment, but no mention was made of envelope opaqueness.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses to follow‐up or exclusions
Selective reporting (reporting bias)	Unclear risk	No outcomes were prespecified in the methods; no access to trial protocol to further assess selective reporting
Other bias	Low risk	Appeared to be free of other bias

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Egarter 1989.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 345 Setting: Vienna, Austria Study date: not reported Inclusion criteria Length of pregnancy established by early ultrasound Membranes intact Cervix favourable for induction (modified Bishop score of > 4) GA at intervention: 40 completed weeks ("at due date") Approximately half the women were primiparous Exclusion criteria Any fetal or maternal risk factors based on history, gynaecological/obstetrical investigation, CTG and routine lab results State of cervix: favourable (Modified Bishop score > 4)
Interventions	Induction group (n = 180): vaginal PE2 (3 mg) tablets repeated 6 and 24 hours later if no active labour versus EM group (n = 165): spontaneous labour awaited until 42 weeks. NST monitoring every 2‐3 days
Outcomes	Mother: birth interval (onset of contractions to birth in hours); rate and indication for operative birth; length of labour; analgesia requirements; caesarean section Baby: birthweight; length of baby at birth; incidence of meconium‐stained amniotic fluid; Apgar scores; results of umbilical cord pH determination; perinatal death
Notes	Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not reported.
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	8/180 women in the induction group refused to be induced; and 3/165 women in the expectant group requested induction; and these 11 women were excluded from analysis post‐randomisation.
Selective reporting (reporting bias)	High risk	No outcomes were prespecified in the methods, limited information was provided for some outcomes, e.g. "The incidence of prolonged labor was not different in both groups... both groups required analgesic treatment in 35%... Birthweight and length, the incidence of meconium‐stained amniotic fluid, of low Apgar scores, and the results of pH determination were not different between the two groups."
Other bias	Unclear risk	Some imbalance in the numbers randomised to each group (180 versus 165)

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Gelisen 2005.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 600 Setting: teaching hospital in Ankara, Turkey; Study date: not reported Inclusion criteria Singleton pregnancy Vertex presentation Intact membranes Bishop score of < 5 Absence of spontaneous uterine contractions (< 4 per hour) Estimated fetal body weight < 4500 g Reactive NST Amniotic fluid index ≥ 5 cm GA at intervention: 41 completed weeks (287 days +/‐ 1 day) Exclusion criteria Allergic to prostaglandins Previous caesarean section Non‐cephalic presentation Body mass index 30 or more before conception Parity 5 or more Low‐lying placenta Previous labour induction attempt State of cervix: unfavourable ‐ Bishop score < 5 Just under half the women were nulliparous.
Interventions	Induction group: labour induction (3 methods) (1) vaginal administration of 50 mg misoprostol (n = 100) (2) oxytocin induction (n = 100), and (3) transcervical insertion of a Foley balloon (n = 100) versus EM group: spontaneous follow‐up with twice‐weekly nonstress testing and amniotic fluid measurement and once‐weekly biophysical scoring (n = 300); 24% of women were induced after 42 completed weeks. the 3 induction arms were combined for analyses
Outcomes	Mother: oligohydramnios; pre‐eclampsia; tachysystole; hyperstimulation; vaginal birth; caesarean (emergent abdominal birth for worrying FHR); failed IOL Baby: perinatal death; shoulder dystocia; meconium stained amniotic fluid; meconium aspiration syndrome; fetal anomaly; low Apgar scores (< 7 at 5 minutes); umbilical artery pH < 7.16; NICU admission; fetal macrosomia; birthweight; birthweight > 4000 g; length of hospital stay
Notes	Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not reported.
Allocation concealment (selection bias)	Unclear risk	Allocation concealment was by sealed, opaque envelopes but there was no mention of numbering and sequential opening of the envelopes.
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding: "Staff members in charge of labor were not blinded to the type of medication used for induction".
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses to follow‐up or exclusions
Selective reporting (reporting bias)	Unclear risk	While prespecified outcomes (in the methods) were reported, no access to trial protocol to further assess selective reporting
Other bias	Low risk	Appeared to be free of other bias

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Grobman 2018.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 6106 Setting: 41 hospitals participating in the Maternal‐Fetal Medicine Units Network of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, USA Study date: women recruited March 2014 through August 2017 Inclusion criteria Low risk, defined as absence of any condition considered to be a maternal or fetal indication for birth before 40⁵ weeks Nulliparous Singleton pregnancy GA: 38⁰ weeks to 38⁶ weeks Reliable information on the length of gestation Vertex presentation with no contraindication to vaginal birth and no caesarean birth planned Exclusion criteria GA at date of first ultrasound > 20⁶ weeks Plan for IOL prior to 40⁵ weeks Plan for caesarean birth or contraindication to labour Breech presentation Signs of labour Fetal demise or known major fetal anomaly Heparin or low‐molecular weight heparin use during the current pregnancy Placenta praevia, accreta, vasa praevia Active vaginal bleeding greater than bloody show ROM Cerclage in current pregnancy Known oligohydramnios, defined as amniotic fluid index < 5 cm or maximal vertical pocket < 2 cm Fetal growth restriction, defined as EFW < 10th percentile Known HIV positivity (due to modified delivery plan) Major maternal medical illness associated with increased risk for adverse pregnancy outcome (e.g. any diabetes mellitus, lupus, any hypertensive disorder, cardiac disease, renal insufficiency) Refusal of blood products Participation in another interventional study that influenced management of labour at delivery or perinatal morbidity or mortality Birth planned elsewhere at a non‐Network site State of cervix: favourable and unfavourable (at the time of randomisation, 63% of the participants had an unfavourable modified Bishop score (i.e. a score < 5))
Interventions	Induction group (n = 3062): women were assigned to undergo IOL at 39⁰ weeks to 39⁴ weeks; with no specific induction protocol mandated. Supplementary Appendix for the manuscript indicated that oxytocin was used, and for women with an unfavourable cervix, cervical ripening was used (actual method left to the discretion of the woman's obstetric provider), in conjunction with or followed by oxytocin; mechanical ripening using a Foley catheter without saline infusion and without concurrent oxytocin was permitted; although not mandated, it was suggested that women should be allowed at least 12 hours in the latent phase after completion of any ripening, ROM, and use of oxytocin before the induction was considered 'failed' (and subsequent caesarean birth) versus EM group (n = 3044): women were asked to forgo elective birth before 40⁵ weeks and to have birth initiated no later than 42² weeks. A specific induction protocol was not mandated for women who underwent induction in either group.
Outcomes	Mother: caesarean section; operative vaginal birth; perineal trauma (third‐ or fourth‐degree perineal laceration); postpartum haemorrhage; breastfeeding (at 4‐8 weeks after birth); length of maternal hospital stay (days, categories including < 2, 2, 3, 4, > 4) Baby: perinatal death (antenatal stillbirth and neonatal death); stillbirth; neonatal death; admission to NICU (intermediate or intensive care unit); neonatal convulsions (seizures); neonatal hypoxic‐ischaemic encephalopathy; pneumonia (confirmed); meconium aspiration syndrome; Apgar score (≤ 3 at 5 minutes); length of neonatal hospital stay (days, categories including < 2, 2, 3, 4, > 4)
Notes	Funding: Eunice Kennedy Shriver National Institute of Child Health and Human Development. Declarations of interest: "Dr. Silver reports receiving consulting fees from Gestavision. No other potential conflict of interest rel avant to this article was reported."
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Prepared by an independent data coordinating centre, using the simple urn method, with stratification according to clinical site
Allocation concealment (selection bias)	Low risk	Randomisation sequence prepared by an independent data coordinating centre, and an internet‐based randomisation system was used.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not feasible
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	For neonatal primary outcomes requiring review, "Reviewers were unaware of the trial‐group assignments". Unclear whether any other outcomes were assessed blind, though discussion reported that "because masking was not feasible, ascertainment bias is possible".
Incomplete outcome data (attrition bias) All outcomes	Low risk	3059/3062 women assigned to induction were included in analyses (1 lost to follow‐up; 2 withdrew consent); 3037/3044 women assigned to control included in analyses (2 lost to follow‐up; 5 withdrew consent)
Selective reporting (reporting bias)	Low risk	Comprehensive range of outcomes specified in protocol and reported
Other bias	Low risk	Note: authors noted report that 184/3059 women (6%) in the induction group, and 140/3037 (4.6%) women in the control group did not birth 'per protocol'.

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Hannah 1992.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 3418 enrolled (data available for 3407 women only) Setting: 22 hospitals across Canada Study date: study conducted between November 1985 and December 1990 Inclusion criteria GA at intervention: 41 completed weeks or more Singleton pregnancy Mixed parity (60% primiparous, 40% multiparous) Exclusion criteria Cervix dilated ≥ 3 cm GA ≥ 44 weeks Non‐cephalic presentation Evidence of a lethal congenital anomaly Maternal diabetes mellitus Pre‐eclampsia Intrauterine growth restriction Prelabour rupture of the membranes Need for urgent birth (e.g. fetal distress or antepartum bleeding) Vaginal birth contraindicated (e.g. placenta praevia) Previous caesarean section Addiction to drugs or alcohol State of cervix: unfavourable at trial entry (first ripening and then IOL in the intervention group)
Interventions	Induction group (n = 1701): up to 3 x 0.5 mg doses of PGE2 gel administered intracervically (if NST was normal and cervix unfavourable at time of induction = 77% of women), followed by either AROM or IV oxytocin infusion, or both versus EM group (n = 1706): daily fetal movement counting, NST and amniotic fluid measurement 2‐3 times per week. If either the NST or amniotic fluid volume assessment was abnormal, or other complications developed, labour was induced (28% of women induced in the expectant group received some form of PE2 (not gel)).
Outcomes	Mother: caesarean section; operative vaginal birth Baby: perinatal death (stillbirth or neonatal death before discharge excluding deaths caused by lethal congenital anomalies); birthweight > 4000 g; Apgar score < 7 at 5 minutes; asphyxial encephalopathy (seizures, alterations in levels of consciousness or tone, or a need for tube feeding during the first 48 hours of life), respiratory distress (oxygen requirement > 40% and respiratory rate > 60 breaths/minute, both within 12 hours after birth and persisting for more than 24 hours, or assisted ventilation for more than 24 hours): meconium aspiration syndrome; neonatal trauma; NICU admission
Notes	Most women (89%) were enrolled at 41⁰ to 41⁶ weeks' gestation (3% before 41 weeks and 8% at or beyond 42 weeks), of whom 86.2% in the induced group and 63.6% in the expectant group gave birth before 42 weeks' gestation. In the induction group, 31% of women were not induced and in the EM group, 34% of women were induced. Funding: Medical Research Council of Canada: MA‐8472; Upjohn Company of Canada supplied the prostaglandin gel. Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not reported.
Allocation concealment (selection bias)	Low risk	Randomisation was carried out at a site separate from the trial ("centrally controlled at McMaster University").
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	The study was partially blinded; an adjudication of abnormal neonatal outcomes was undertaken by a neonatologist who was unaware of the mothers' group assignments.
Incomplete outcome data (attrition bias) All outcomes	Low risk	3418 women enrolled (data available for 3407 women); 7 women whose babies had lethal congenital anomalies were excluded after randomisation from the analysis of perinatal and neonatal outcomes ‐ induction group (1 woman) and EM group (6 women).
Selective reporting (reporting bias)	Unclear risk	Prespecified outcomes (from the methods) were reported; some results reported incompletely in text, e.g. "The frequency of postpartum maternal morbidity (hemorrhage, sepsis, endometritis) did not differ between the two groups (data not shown)". No access to trial protocol to further assess selective reporting
Other bias	Low risk	Appeared to be free of other bias; although methods of induction differed between the induction group and the women requiring induction in the EM group.

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Heimstad 2007.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 508 Setting: St. Olavs University Hospital, Trondheim, Norway Study date: women randomised between September 2002 and July 2004 Inclusion criteria Singleton pregnancies GA: 41+ weeks (at intervention GA = 40⁶ and beyond) Cephalic presentation No PROM Primiparous (46%) and multiparous State of cervix: all stages included
Interventions	Inductiongroup (n = 254): if cervix favourable (Bishop score ≥ 6) AROM + oxytocin, if not (Bishop score < 6) 50 µg misoprostol vaginally versus EM group (n = 254): twice‐weekly ultrasound and CTG, labour induction after 300 days of pregnancy
Outcomes	Mother: prolonged labour; mode of birth; perineal trauma; maternal satisfaction; postpartum haemorrhage Baby: perinatal death; neonatal morbidity, for which a score was tallied (by evaluating the degree of deviation from the potential of a perfect outcome for each newborn as defined by the authors); neonatal trauma; birthweight; birthweight > 4000 g, NICU admission, birth asphyxia, meconium aspiration syndrome, Apgar < 7 at 5 minutes
Notes	Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computerised randomisation using blocks of 16 with no stratification
Allocation concealment (selection bias)	Low risk	Central allocation ‐ clinical trials office
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No women were lost to follow‐up for clinical outcomes; 8 women did not complete the inclusion questionnaire; for the post‐birth telephone survey, 12 women were lost to follow‐up (4 in induction group and 8 in EM group).
Selective reporting (reporting bias)	Unclear risk	While all prespecified outcomes (in the methods) were reported, with no access to trial protocol, it was not possible to further assess selective reporting.
Other bias	Low risk	Appeared to be free of other bias

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Henry 1969.

*Study characteristics*
Methods	RCT with inadequately reported randomisation methods
Participants	Number of women randomised: 112 Setting: Birmingham, UK Study date: not reported Inclusion criteria (not well specified) GA: 41⁺ weeks Certain of dates Primiparous and multiparous women Exclusion criteria Not specified State of cervix: Not mentioned as a criterion
Interventions	Induction group (n = 55): AROM and oxytocin ("surgical" group) versus EM group (n = 57): weekly amnioscopy
Outcomes	Mother: number of days past term; prolonged labour; mode of birth Baby: perinatal death; birthweight
Notes	4 women in expectant group and 1 in induction group were randomised before 41 weeks. Funding: not reported Declaration of interests: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not reported.
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses to follow‐up or exclusions
Selective reporting (reporting bias)	Unclear risk	No outcomes were prespecified in the methods; no access to trial protocol to further assess selective reporting
Other bias	Low risk	Appeared to be free of other bias

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Herabutya 1992.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 108 Setting: Bangkok, Thailand Study date: study conducted July 1987 to January 1991 Inclusion criteria Certain dates Low risk GA at intervention: 42 completed weeks (immediately after) > 80% women nulliparous Exclusion criteria Women with Bishop scores of > 6 were judged to have a favourable cervix and were excluded from the study State of cervix: unfavourable cervix (Bishop score 6 or less)
Interventions	Induction group (n = 57): PGE2 intracervical, repeated after 6 hours, AROM and oxytocin on day 2 according to contractions versus EM group (n = 51): a) NST between 42 and 43 completed weeks. 2) NST between 43 and 44 completed weeks; women underwent IOL if there were abnormalities in antepartum fetal testing as non‐reactive NST, or variable decelerations on NST or if Bishop score > 6 on reaching 44 completed weeks' gestation
Outcomes	Mother: length of first stage of labour; mode of birth; cephalopelvic disproportion; fetal distress Baby: birthweight; meconium staining; Apgar score < 7 at 1 minute; Apgar score < 7 at 5 minutes; intubation required; admission to special care baby unit; perinatal death
Notes	Funding: Ramathibodi Hospital Research Fund Grant 1988 Declaration of interests: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not reported.
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses to follow‐up or exclusions
Selective reporting (reporting bias)	Unclear risk	No outcomes were prespecified in the methods; no access to trial protocol to further assess selective reporting
Other bias	Low risk	Appeared to be free of other bias

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James 2001.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 74 Setting: Vellore, India Study date: not reported Inclusion criteria Low‐risk women Singleton pregnancy Cephalic presentation GA: 41 completed weeks (287 days) Exclusion criteria Presence of risk factors known to increase perinatal death and morbidity such as chronic hypertension, pre‐eclampsia, maternal diabetes mellitus, fetal growth restriction, multiple gestation, hydramnios, PROM, antepartum haemorrhage and previous caesarean section State of cervix: not mentioned as a criterion
Interventions	Induction group (n = 37): Bishop < 5: cervical ripening with extra‐amniotically placed 16F Foley catheter with 20 mL of saline Bishop > 5: stripping of membranes Then, 12 hours later, IOL by AROM and oxytocin infusion versus EM group (n = 37): daily fetal movement counts; biophysical profile every second day
Outcomes	Mother: mode of birth and indications; duration of labour; mean hospital stay Baby: meconium staining of amniotic fluid; meconium aspiration; Apgar scores < 7 (at 1 and 5 min); need for neonatal intubation; birthweight; birthweight > 4000 g; signs of post‐maturity; perinatal deaths; abnormal electronic fetal trace monitoring
Notes	Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	A table of random numbers was used.
Allocation concealment (selection bias)	Unclear risk	Allocation concealment was unclear since "... a series of consecutively numbered, sealed envelopes..." was used but no mention was made of opaqueness of the envelopes.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No loss to follow‐up or post‐randomisation exclusion
Selective reporting (reporting bias)	Unclear risk	All of the outcomes mentioned in the methods section were reported on in the results section; mean duration of labour was reported with no measure of variance. No access to trial protocol to further assess selective reporting
Other bias	Low risk	Appeared to be free of other bias

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Keulen 2019.

*Study characteristics*
Methods	Multicentre RCT (non‐inferiority trial)
Participants	Number of women randomised: 1815 randomised Setting: 123 primary care midwifery practices and 45 hospitals (secondary care) equally distributed across the Netherlands Study date: study conducted 2012‐16 Inclusion criteria: Low‐risk, uncomplicated singleton pregnancy Fetus in stable cephalic position Certain GA of 40⁵ to 41⁰ weeks with no contraindications to EM until 42 weeks Just over half the women were nulliparous Exclusion criteria: Age < 18 years ROM, or in labour, or both Non‐reassuring fetal status (e.g. no fetal movements, abnormal fetal heart rate and/or expected IUGR) Known fetal anomalies (including abnormal karyotype) that could influence perinatal outcome Contraindications to induction (including previous caesarean) Contraindications to EM (e.g. pregnancy‐induced hypertension) State of cervix: mixed ‐ in both groups three‐quarters of the women had a Bishop score < 6 at study entry
Interventions	Induction group (n = 907): Women were scheduled for induction at 41⁰ weeks to 41¹ weeks. All women were primed or induced, or both according to local protocols. Women with a Bishop score < 6 received cervical priming with PGE1 (misoprostol, oral or vaginal), PGE2 (dinoprostone), Foley catheter or double balloon catheter, or a combination of these until AROM could be performed. AROM was followed by IV oxytocin if required. versus EM group (n = 908): women awaited spontaneous onset of labour until 42⁰ weeks in their initial care setting (primary or secondary), with monitoring according to local protocol. which typically involved a combination of CTG, and sonographic assessment of amniotic fluid in secondary care at 41‐42 weeks. Women with ongoing pregnancies were scheduled for induction at 42⁰ weeks in secondary care, following a similar induction protocol to the intervention group.
Outcomes	Mother: caesarean section; operative vaginal birth; analgesia used (reports on pain treatment during labour, and specifically on remifentanil, pethidine/promethazine/other opiates, epidural anaesthesia, other); perineal trauma (episiotomy (without tear), obstetrica anal sphincter injuries, third‐degree tear, fourth‐degree tear, episiotomy and third‐degree tear, episiotomy and fourth‐degree tear); postpartum haemorrhage (≥ 1000 mL); Baby: perinatal death; stillbirth; neonatal death; NICU admission; meconium aspiration syndrome; Apgar score < 7 at 5 minutes; birthweight
Notes	Funding: grant from the Netherlands Organisation for Health Research and Development ZonMw (grant No 171202008) Declarations of interest: "BWM is supported by a National Health and Medical Research Council practitioner fellowship (GNT1082548) and reports consultancy for ObsEva, Merck, and Guerbet; no support from any other organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years, no other relationships or activities that could appear to have influenced the submitted work."
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Web‐based program (ALEA) using randomly permuted block sizes of 4 and 2, stratified by centre
Allocation concealment (selection bias)	Low risk	Central (web‐based) randomisation
Blinding of participants and personnel (performance bias) All outcomes	High risk	Women and staff were aware of assignments.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	‘"he statistician who performed the analyses was blinded to the allocation of the participants and performed the analysis according to a predefined analysis plan."
Incomplete outcome data (attrition bias) All outcomes	Low risk	900/907 women allocated to induction were analysed in ITT analyses (7 were excluded – 1 withdrew consent, and 6 were not eligible); 901/908 women allocated to EM were analysed in ITT analyses (7 were excluded due to ineligibility).
Selective reporting (reporting bias)	Low risk	Wide range of outcomes reported, as specified in published protocol.
Other bias	Unclear risk	"Since in our trial all women in the 41 week induction group received obstetrician led intrapartum secondary care whereas in the expectant management group until 42 weeks 68.7% of the women received midwifery led primary care at start of labour and 34.3% at time of birth, it could be suggested that our study is prone to performance bias (different care) and measurement bias (different assessment of neonates)."

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Martin 1978.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 264 "admitted to this trial" Setting: Royal Maternity Hospital, Northern Ireland, UK Study date: not reported Inclusion criteria GA: women in their 38th week of pregnancy All past/present pregnancies obstetrically normal Booked before 18th week Menstrual cycle not exceeding 35 days No contraceptive pill taken, nor any pregnancy for at least 3 months before the LMP Size of uterus at booking corresponded to the period of amenorrhoea Primiparous and multiparous women Exclusion criteria Not described State of cervix: not clearly reported; assumed to be mixed (Bishop score recorded).
Interventions	Induction group (n = 131 admitted; 92 analysed): IOL at 39 weeks' GA. Women were admitted for fasting at 8:30 am; their forewaters were punctured soon after and Bishop score and cervical dilatation recorded. IV oxytocin commenced at 2.5 mU/minute and doubled every 30 minute until satisfactory uterine response achieved; dose varied to maintain adequate contractions. All women continuously monitored with internal tocography and fetal scalp electrode. versus EM group (n = 133 admitted; 92 analysed): await spontaneous labour until 42 weeks, unless IOL required earlier for medical reasons. Women had, if necessary, augmentation of labour by puncture of the forewaters or IV oxytocin; when possible, they were also monitored.
Outcomes	Mother: mode of birth (assisted birth; caesarean birth); induction to birth interval; unexplained postpartum pyrexia; analgesia demand; type 1 and 2 diabetes; meconium staining of the amniotic fluid; duration of gestation; attitudes towards management Baby: Apgar scores at 1 and 5 minutes; Dubowitz scores < 45; stillbirth; hyperbilirubinaemia
Notes	Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"A prospective randomized controlled trial"; "allocated using random number tables."
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	“All monitor records were examined blind at completion of the trial.”
Incomplete outcome data (attrition bias) All outcomes	High risk	184/264 women followed up (30% loss to follow‐up). 264 women eligible, 34 excluded: induction group: obstetric abnormality (8 women); refusal (10 women); defaulter (6 women); spontaneous labour before attending clinic (1 woman). EM group: obstetric reasons (9); leaving 230 women in the trial (106 in planned birth, 124 in EM group) Of the 106 women in the induction group, 13 went into spontaneous labour before the date of admission and 1 was excluded due to medical reasons – therefore 92 women were induced and analysed. Of the 124 women in the EM group, a further 32 were excluded due to obstetric abnormalities or failure to go into spontaneous labour before 42 weeks – therefore only 92 were analysed.
Selective reporting (reporting bias)	Unclear risk	Some results reported incompletely, e.g.: “There was no difference with respect to the distribution of Apgar scores…at five minutes.”
Other bias	Unclear risk	Groups appeared comparable at baseline however analyses excluded 30% of women admitted to the trial. Limited methodological detail provided to further assess other bias

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Martin 1989.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 22 Setting: Jackson, USA Study date: women recruited 1 July 1987 to 31 January 1988 Inclusion criteria GA: 41 completed weeks Reliable dates Primiparous and multiparous women Exclusion criteria Oligohydramnios with < 1 cm pocket of amniotic fluid in any dimension A non‐reactive NST Positive concentration stress test Bishop score > 5 State of cervix: unripe (Bishop score 5 or less) included
Interventions	Induction group (n =12): laminaria tents followed by oxytocin versus EM group (n = 10): weekly ultrasound for amniotic fluid assessment and NST
Outcomes	Mother: mode of birth; length of labour; type of analgesia; length of hospital stay; labour‐associated morbidity Baby: birthweight; Apgar score; perinatal deaths; neonatal course; meconium staining
Notes	Funding: Vicksburg Hospital Medical Foundation Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not reported.
Allocation concealment (selection bias)	Unclear risk	Allocation in sealed envelopes but no mention of opaqueness, numbering and sequential opening of envelopes.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses to follow‐up or exclusions.
Selective reporting (reporting bias)	High risk	No outcomes were prespecified in the methods; a number of outcomes reported without measures of variance (e.g. birthweight, length of labour, hospital stay), and thus these outcomes could not be used in the meta‐analyses. No access to protocol to further assess selective reporting
Other bias	Low risk	Appeared to be free of other bias

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Miller 2015.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 162 Setting: Military tertiary care medical centre, USA Study date: women randomly assigned March 2010 to February 2014 Inclusion criteria GA: between 38⁰ and 38⁶ weeks 18 years or older Nulliparous Singleton pregnancies, cephalic presentation Modified Bishop score ≤ 5 Exclusion criteria Contraindications to vaginal birth Unclear GA Requiring IOL for medical or obstetric indications ≤ 39 weeks' GA Non‐English speaking State of cervix: modified Bishop score ≤ 5
Interventions	Induction group (n = 82): IOL ≤ 1 week of randomisation; not before 39 weeks' GA Where possible, IOL by Foley catheter (single balloon, 60 mL water), taped in place until expulsion or 12 hours. After Foley catheter, oxytocin (2 mIU per min, increasing every 20 minute to 36 mIU per minute max) until adequate contractions. If Foley catheter placement not possible, IOL by misoprostol 25 µg vaginally, repeated every 4 hours; AROM after 3 cm dilation; oxytocin administered after last if adequate contractions not observed with misoprostol versus EM group (n = 80): scheduled for routine appointments and birthed for obstetric indications no later than 42 weeks' GA
Outcomes	Mother: caesarean birth; mode of birth; number of visits after randomisation; unscheduled clinic or triage visits; number of antepartum fetal testing appointments; GA at admission; Bishop score at admission; admission diagnosis; indication for operative birth; use of regional anaesthesia; chorioamnionitis; EBL; blood transfusion; endomyometritis; labour and birth length of stay; postpartum stay Baby: meconium‐stained amniotic fluid; NICU admission; birthweight; SGA; LGA; Apgar score < 5 at 5 minutes
Notes	Funding: not reported Declarations of interest: the authors declared that they had no financial conflicts of interest.
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated list of random numbers in permuted blocks of 4
Allocation concealment (selection bias)	Low risk	Allocation was concealed by the use of opaque, sealed, sequentially numbered envelopes.
Blinding of participants and personnel (performance bias) All outcomes	High risk	No blinding: "blinding of health care providers to the indication for delivery was deemed impractical."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Low loss to follow‐up following randomisation (82/82 and 79/80 women included in the analyses)
Selective reporting (reporting bias)	Unclear risk	No access to trial protocol to assess selective reporting. Perinatal death not reported
Other bias	Low risk	Appeared to be free of other bias

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NICHHD 1994.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 440 Setting: University hospitals in the USA Study date: Women screened December 1987 to July 1989 Inclusion criteria GA at trial entry: at least 287 days GA at intervention: 41 to 43 completed weeks (at least 287 days to < 301 days) ~60% primiparous Exclusion criteria Any medical or obstetric complications requiring IOL, caesarean section or frequent monitoring of maternal or fetal condition State of cervix: unfavourable (Bishop score 6 or less)
Interventions	Induction group (n = 174): cervical priming with PGE2 gel followed 12 hours later with oxytocin versus EM group (n = 175): weekly cervix assessments, twice weekly NST and amniotic fluid volume assessment A total of 265 women were randomised to the intervention arm; however, 91 of these women were randomised to placebo gel with oxytocin 12 hours later and these women have not been included in this review.
Outcomes	Mother: time to birth from randomisation; maternal infection; need for transfusion; uterine hyperactivity; mode of birth; maternal death Baby: mechanical ventilation; nerve injury; seizures; babies with ≽1 adverse outcome; perinatal death; birthweight; Apgar score < 4 at 5 minutes; late decelerations in labour; meconium in amniotic fluid; meconium in aspiration pneumonia
Notes	The initial sample size intended was 2800. However, after 18 months and 440 participants, the study was stopped, since the incidence of adverse outcome was only 1.1% and therefore a sample size of 5600 would be required to adequately test the hypothesis proposed. Funding: National Institute of Child Health and Human Development, NIH, USA Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The randomisation sequence generation was performed using a computer‐generated randomisation scheme stratified by site and GA.
Allocation concealment (selection bias)	Low risk	Allocation was concealed by using central allocation by a data co‐ordinating centre.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses to follow‐up or exclusions
Selective reporting (reporting bias)	Unclear risk	All prespecified outcomes (in methods) were reported; no access to trial protocol to further assess selective reporting
Other bias	Low risk	Appeared to be free of other bias

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Nielsen 2005.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 226 Setting: Army Medical Center, Tacoma, Washington, USA Study date: enrolled September 1999 to December 2002 Inclusion criteria GA at intervention: 39‐40 weeks Cephalic presentation Singleton gestation Maternal age of greater than 17 years Candidate for vaginal birth Semi‐favourable cervical Bishop score defined as a score of 5 or greater in nulliparous or 4 or greater in multiparous women Exclusion criteria No additional criteria reported State of cervix: favourable (≥ 5 for nulliparous and ≥ 4 for multiparous women)
Interventions	Induction group (n = 116): AROM, oxytocin or both versus EM group (n = 110): weekly follow‐up until 42 weeks. Labour induced after 42 weeks. Weekly monitoring with CTG and ultrasound, increased to twice a week after 41 weeks.
Outcomes	Mother: randomisation to birth interval; admission to birth interval; Indication for admission; epidural analgesia; mode of birth; EBL; length of labour; chorioamnionitis; postpartum days Baby: birthweight; admission to NICU; Apgar score < 7 at 5 minutes
Notes	The study was discontinued after recruitment of 226 women (target of 600) due to slow recruitment and no observed difference in the 2 groups. Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The randomisation sequence was generated using a computer‐generated list.
Allocation concealment (selection bias)	Low risk	Allocation concealment was achieved using sequentially numbered, opaque, sealed envelopes.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses to follow‐up or exclusions. 23/116 (19.8%) in induction group went into spontaneous labour, 10/110 (9.1%) in the EM group required labour induction and results for these women were analysed according to which group they were randomised.
Selective reporting (reporting bias)	Unclear risk	No access to trial protocol to confidently assess selective reporting. Perinatal death not reported
Other bias	Unclear risk	Baseline imbalance for Bishop score "The only significant difference noted was EM patients had a more favorable Bishop score on admission than IND patients (7.2 + 2.1 versus 8.6 + 2.0, P < 0.0001)."

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Ocon 1997.

*Study characteristics*
Methods	RCT (partially translated).
Participants	Number of women randomised: 113 Setting: Gran Canaria, Spain Study date: not reported Inclusion criteria Unknown due to not being fully translated GA at intervention: 42 completed weeks Exclusion criteria Unknown, not in translation State of cervix: unfavourable (Bishop score < 5)
Interventions	Induction group (n = 57): intracervical PGE2 gel (0.5 mg); unclear whether further intervention occurred (full translation not available) versus EM group (n = 56): monitoring by NST, biophysical profile and amnioscopy
Outcomes	Mother: time to birth; mode of birth Baby: meconium staining; NICU admission; birthweight > 4000 g; Apgar score < 7 at 5 minutes (other outcomes may have been present, but were not reported in the translation)
Notes	Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not reported according to the translation.
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported according to the translation.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses to follow‐up or exclusions
Selective reporting (reporting bias)	Unclear risk	No access to trial protocol to confidently assess selective reporting. Perinatal deaths appeared not to have been reported according to the translation, although this has not been verified by a second translation.
Other bias	Low risk	Appeared to be free of other bias

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Roach 1997.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 201 Setting: Hong Kong, China Study date: not reported Inclusion criteria GA: 41 weeks at recruitment GA at intervention: 42 completed weeks Parity: not stated Exclusion criteria Pre‐eclampsia Gestational diabetes Contraindication to vaginal birth (e.g. placenta praevia, non‐cephalic presentation) Evidence of fetal or maternal compromise State of cervix: not mentioned as a criterion
Interventions	Induction group (n = 96): PGE2 pessaries 6‐hourly if necessary versus EM group (n = 105): serial monitoring with NST (x 2) and amniotic fluid index measurements (x 1) weekly
Outcomes	Mother: spontaneous labour; caesarean section; fetal distress in labour Baby: birthweight; Apgar score < 7 (1 minute/5 minutes); cord blood pH; admission to NICU; meconium below the vocal cords
Notes	Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generation was not reported.
Allocation concealment (selection bias)	Unclear risk	Allocation in a series of identical envelopes but no mention of sealed envelopes, opaqueness and sequential numbered envelopes
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses to follow‐up or exclusions. 17/96 (18%) in the induction group went into spontaneous labour and 12/105 (11%) in the EM group were induced and the results for these women were included in the analyses.
Selective reporting (reporting bias)	Unclear risk	Very few outcomes reported; "We did not address perinatal mortality in this study." No access to trial protocol to further assess selective reporting
Other bias	Low risk	Appeared to be free of other bias

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Sahraoui 2005.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 150 Setting: Sousse, Tunisie (Tunisia) Study date: not reported Inclusion criteria 41⁰ to 41⁶ weeks Dates concur with ultrasound before 20 weeks Regular menstrual cycle length 28‐30 days Not on contraception for 3 months prior to conception Singleton pregnancy Morphologically normal ultrasound Intact membranes Bishop score < 4 at initial exam No medical or obstetric complications(?) Exclusion criteria Presence of risk factors for complication (hypertension, pre‐eclampsia, diabetes, placenta praevia) Fetal‐pelvic disproportion More than 5 previous pregnancies Previous caesarean section Previous IUFD Medical contraindication to the use of prostaglandins (asthma, glaucoma, heart disease, allergy to prostaglandins) State of cervix: cervix unripe (Bishop score < 4)
Interventions	Induction group (n = 75): PGE2 gel intracervically (daily cervical ripening by PGE2 gel, maximum 3 gels) versus EM group (n = 75): CTG every second day until 42 completed weeks. After that, PGE2 gel if no spontaneous labour
Outcomes	Mother: duration of labour; mode of birth; GA at birth; duration of mother’s hospital stay (hours); need for augmentation of labour using synthetic oxytocin (Recours aux ocytociques); effect of Bishop score on admission on duration of labour (Effet du score de Bishop à l’admission sur la durée (duration) du travail (labour); progress in labour; time between final dose of PE2 gel and birth Baby: duration of infant’s hospital stay (hours); total cost of care; admission to neonatal unit; stained amniotic fluid; Apgar score at 1 minute; perinatal death; stillbirth; neonatal death; macrosomia; signs of post‐maturity; need for resuscitation at birth; number of doses of gel administered
Notes	This article is in French. Funding: not reported Declaration of interests: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation by computer
Allocation concealment (selection bias)	Unclear risk	Article in French. Appeared not to have been reported
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No apparent losses to follow‐up or exclusions
Selective reporting (reporting bias)	Unclear risk	No access to trial protocol to confidently assess selective reporting
Other bias	Low risk	Appeared to be free of other bias

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Sande 1983.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 166 Setting: Ulleval Hospital, Norway Study date: not reported Inclusion criteria GA: between 40 and 41 weeks Normal pregnancy Vertex presentation Singleton fetus Bishop score 5 points or more Exclusion criteria Not described State of cervix: Bishop score ≥ 5
Interventions	Induction group (n = 76): IOL on the following morning after randomisation; IV oxytocin (10 units in 1 L 5% glucose) immediately following AROM. Women were monitored by CTG versus EM group (n = 90): waited for spontaneous labour to occur, following the normal procedure for the department (labour was induced after 42 weeks)
Outcomes	Mother: duration of first and second stages of labour; pain relief; mode of birth (caesarean birth; vacuum; forceps; spontaneous birth); postpartum bleeding; induction to birth interval Baby: liveborn; neonatal death; birthweight; Apgar scores at 1 and 5 minutes; morbidity (transfer to NICU; paediatric examination of 1st and 5th day)
Notes	Only data for perinatal death, stillbirth and neonatal death included in meta‐analyses
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generated was not reported.
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	High risk	Per protocol analysis performed. Of the 76 women randomised to the induction group, 23 birthed spontaneously before induction In the EM group, 15 of the 90 women passed 42 weeks and had their labour induced. Therefore, there were a total of 68 women who had their labour induced, and 98 birthed spontaneously (results analysed as such, not as per randomisation).
Selective reporting (reporting bias)	High risk	A number of outcomes such as birthweight, postpartum bleeding, and neonatal morbidity were reported incompletely in the text, e.g. “no differences” and “ns.”
Other bias	Unclear risk	No information by randomisation group

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Sargunam 2019.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 318 Setting: University hospital in Malaysia Study date: recruitment 5 June 2015 to 10 November 2017 Inclusion criteria: GA: ≥ 39 weeks* (≥ 273 days); prolonged latent phase of labour (defined as an overnight hospitalisation of at least 8 hours), persistent contractions of at least 1 in 30 minutes, cervical dilation ≤ 3 cm and intact membranes, nulliparous (no prior pregnancy > 20 weeks), a singleton fetus, cephalic presentation, reassuring FHR tracing Exclusion criteria: known fetal abnormalities, estimated fetal weight ≥ 4 kg or ≤ 2 kg (clinical assessment for small or large for GA, if either suspected then ultrasound EFW), contraindications to EM (e.g. pregnancy‐induced hypertension, suspected abruption), previous uterine surgery (e.g. myomectomy or hysterotomy), known prostaglandin allergy or contraindication to vaginal birth State of cervix: mixed, mean Bishop Score 4.3 [1.6] intervention group; 4.1 [1.4] comparator Parity: nulliparous
Interventions	Induction group (n = 158): immediate IOL (with vaginal dinoprostone or amniotomy or oxytocin as appropriate) EM group (n = 160): await labour for at least 24 hours unless indicated intervention as directed by care provider
Outcomes	Mother: caesarean; vaginal birth (including instrumental versus spontaneous); labour duration outcomes (intervention to active phase of labour i.e. cervical dilation ≥ 5 cm and time to birth); epidural analgesia needed, intrapartum oxytocin, titrated oxytocin infusion or vaginal dinoprostone pessary (nonreassuring fetal heart tracing concurrent with uterine tachysystole ≥ 6 contractions in 10 minutes), postpartum haemorrhage (blood loss ≥ 500 mL), women's satisfaction (Likert response) to allocated intervention, during birth and baby outcomes ‐ obtained before hospital discharge Baby: 5 minute Apgar score < 7; cord artery acidosis (pH ≤ 7 and base excess ≤ ‐8 mmol/L; birthweight; admission to NICU; indications for admission
Notes	ISRCTN protocol stated 39‐41 weeks GA; also registered as Malaysian National Medical Research Register NMRR‐15.16‐23,886 Funding:* "This study was internally funded by University of Malaya research grant (BK078‐2015)". Declaration of interests: none declared
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"computer generated random sequence using random.org"
Allocation concealment (selection bias)	Low risk	Web‐based/central randomisation and by an investigator who was not involved in the trial. Participants were randomised by opening the lowest numbered, sealed, opaque envelope remaining.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported ‐ unlikely considering the type of interventions compared
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported ‐ unlikely for most outcomes assessed
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	"318 women were randomized (158 to labor induction and 160 to expectant management). Due to criteria infringements, we excluded nine women allocated to labor induction due to 1) labor induction refusal (four women), 2) membranes already ruptured (three women) and 3) pre‐induction non‐reassuring FHR tracing (two women) and one women assigned to expectant management due to membranes already ruptured". Assessed as unclear due to differential attrition in the 2 groups: 9/158 versus 1/160
Selective reporting (reporting bias)	Low risk	Outcomes specified in prospectively registered protocol reported
Other bias	Low risk	Data reported on key characteristics of participants, indicating few differences between groups

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Suikkari 1983.

*Study characteristics*
Methods	Randomised trial, no further details
Participants	Number of women randomised: 119 Setting: Lappenranta, Finland Study date: recruitment October 1980 to December 1981 Inclusion criteria At least 10 days post‐date Regular menses GA at intervention: 41⁺ weeks Primiparous and multiparous women Exclusion criteria Cases where the fetal biparietal measure different in mid pregnancy ultrasonography by over 10 days from the mean curve were excluded. State of cervix: not used as a criterion
Interventions	Induction group (n = 66): oxytocin alone or with AROM depending on the cervix versus EM group (n = 53): obstetric examination, NST, biochemical tests and amniotic fluid determination every 3 days
Outcomes	Mother: mode of birth (reported only as operative); duration of labour; mean blood loss during labour; maternal death Baby: mean birthweight; Apgar scores; perinatal death; stillbirth; neonatal death
Notes	The study was available as an abstract only. Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generated was not reported.
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient information to determine losses to follow‐up or exclusions
Selective reporting (reporting bias)	Unclear risk	No outcomes were prespecified (abstract).
Other bias	Unclear risk	Unable to identify other bias based on the abstract; some degree of imbalance in numbers randomised to each group (66 and 53).

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Tylleskar 1979.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 112 Setting: Linköping and Motala, Sweden Study date: not reported Inclusion criteria Maternal age 18‐30 years for primipara and 18‐35 years for multipara Regular menstrual period before the pregnancy; LMP normal and date known; women usual hormonal contraceptives had at least 3 normal periods after completing the last course Normal symphysis‐fundus distance and weight gain according to gravidogram Previous pregnancies and births normal (birthweight 3‐4 kg) Actual pregnancy normal and head presentation Normal pelvic outlet on clinical examination Primipara with pelvic score of at least 5 points and engaged head; multipara with pelvic score at least 4 points (within 1 week of due date) GA at intervention: expected day of birth +/‐ 2 days Exclusion criteria Not described State of cervix: primipara with pelvic score of at least 5 points and engaged head; multipara with pelvic score at least 4 points
Interventions	Induction group (n = 57): after AROM, an open‐ended saline‐filled catheter was inserted for measurement of intraamniotic pressure and a scalp electrode applied for continuous recording of FHR. IV oxytocin (using Cardiff Infusion System Mark II) was started 15 minutes later at 1 mU/minute, increased continuously until the intensity of contractions was at least 33 mm Hg, with a frequency of at least 1 contraction every 150 seconds; the infusion rate doubled every 12.5 minutes. versus EM group (n = 55): women were asked to come to the delivery ward as soon as labour started; external CTG recordings were made until definite labour activity was demonstrated. AROM was performed, a catheter and scalp electrode applied when for primipara the cervix was at least 50% effaced and dilated more than 2 cm, and for multipara when the cervix was dilated to 3 cm. If the pregnancy lasted more than 14 days beyond the estimated time of birth labour was induced using IV oxytocin.
Outcomes	Mother: duration of labour; uterine activity at 6 cm cervical dilatation; total amount of oxytocin used; FHR patterns (early decelerations; late decelerations; bradycardia); amount of bleeding during the third stage of labour; mode of birth (vacuum extraction); placental retention; maternal pH at birth; analgesia (pudendal block, nitrous oxide, pethidine/atarax); women's experiences of the birth Baby: birthweight; birth asphyxia; Apgar score at 1 and 5 minutes; baby pH; lowest weight in first week; haemoglobin and haematocrit in umbilical vein and day 2; bilirubin levels day 1‐3; 4 dimensions of the Brazelton Scale
Notes	Funding: not reported Declaration of interests: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method of sequence generated was not reported.
Allocation concealment (selection bias)	Unclear risk	The method of allocation concealment was not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	High risk	112 women were randomised. 13/57 in the induction group and 12/55 in the EM group went into labour before the expected due date and were excluded. 3 further women were excluded – 1 in the EM group birthed rapidly and data collection was not possible; 1 woman in each group had a caesarean due to feto‐pelvic disproportion. Thus 43/57 in the induction group and 41/55 in the EM group were analysed; overall 84/112 (75%).
Selective reporting (reporting bias)	High risk	Results for a number of outcomes are reported incompletely, e.g. "Nor were there any differences in maternal pH at delivery"; "Analgesia in the form of pudendal block or nitrous oxide was given in the same frequency in the two groups;" and "An analysis of the questionnaire with respect to the patients experiences of the delivery indicate a positive attitude... No statistical differences between groups were found."
Other bias	Unclear risk	Limited methodological detail provided. The only baseline characteristics reported were age, pelvic score and number of previous pregnancies, and only for women analysed.

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Walker 2016.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 619 Setting: 39 National Health Service hospitals, UK Study date: women recruited August 2012 to March 2015 Inclusion criteria GA: between 36⁰ and 39⁶ weeks Nulliparous 35 years or older on due date Singleton, live fetus in cephalic presentation Exclusion criteria Pregnancy complicated by known fetal abnormality that would lead to neonatal death Any contraindications to labour, vaginal birth, or EM Undergone myomectomy Uncertain dates (no ultrasound < 22 weeks) Undergone IVF with donor eggs State of cervix: not clearly reported (mixed)
Interventions	Induction group (n = 305): IOL between 39⁰ and 39⁶ weeks, with method dependent on local protocol and cervical ripeness (most participating units used prostaglandin ripening followed, if necessary, by AROM and oxytocin). Prostaglandin tablet regimen (n = 49), prostaglandin gel regimen (n = 63), prostaglandin slow release pessary (N = 158), AROM (n = 129), oxytocin (n = 137) (women could have > 1 intervention) versus EM group (n = 314): waiting for spontaneous onset of labour, unless a situation developed necessitating birth by IOL or caesarean. Women underwent IOL between 41‐42 weeks (7‐14 days after due date) depending on preference and physician's usual practice; if a woman declined induction at 42 weeks, she could undergo a scan to determine fetal growth and amniotic fluid volume daily or every other day, CTG and monitoring according to usual practice.
Outcomes	Mother: caesarean; method of birth; onset of labour; indication for induction; method of induction; indication for caesarean; intrapartum and postpartum complications (e.g. systemic infection, need for blood transfusion); mother’s expectations and experience of childbirth; analgesia; perineal trauma; postpartum haemorrhage Baby: live or stillbirth; birthweight; admission to NICU; birth trauma; 2 composite outcomes for serious neonatal complications (direct trauma and hypoxia); Apgar < 7 at 5 minutes
Notes	Staff were encouraged to use the same methods of IOL in the induction group and the EM group who were subsequently induced. Funding: Grant (PB‐PG‐0610‐22275) from the Research for Patient Benefit Programme of the National Institute for Health Research Declarations of interest: Dr. Smith reported receiving fees for serving on an advisory board from Roche Diagnostics, consulting fees from GlaxoSmithKline, equipment loans from Roche Diagnostics and General Electric, travel support from Roche Diagnostics and Chiesi, and grant support from GlaxoSmithKline and Action Medical Research, and being named as an inventor on a pending patent (PCT/EP2014/062602) filed by GlaxoSmithKline related to retosiban as a preventive treatment for preterm labour in women with increased uterine stretch. No other potential conflict of interest relevant to this article was reported.
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	1:1 ratio using a computer‐generated code with the use of permuted blocks of randomly varying size generated by a clinical trials unit. Stratified by trial centre and maternal age
Allocation concealment (selection bias)	Low risk	Allocation was concealed by using central allocation by the Clinical Trials Unit
Blinding of participants and personnel (performance bias) All outcomes	High risk	Blinding was not feasible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Analysis included all but 1/619 women; 83% completed childbirth experience questionnaires
Selective reporting (reporting bias)	Low risk	Trial protocol published
Other bias	Low risk	Appeared to be free of other bias

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Wennerholm 2019.

*Study characteristics*
Methods	Multicentre RCT: ISRCTN26113652
Participants	2760* healthy women ≥ 18 years old with a singleton pregnancy in cephalic presentation at 41+⁰ weeks Setting: 14 hospitals in Sweden. Study date: recruitment 20 May 2016 to 13 October 2018. Trial undertaken within the Swedish Network for National Clinical Studies within Obstetrics and Gynaecology (SNAKS) Inclusion criteria: women 18 years or older, able to understand oral and written information, cephalic presentation at 40 + 6 to 41 + 1 weeks according to ultrasound based dating in first or second trimesteror for pregnancies after assisted reproduction according to day of oocyte retrieval Exclusion criteria: previous caesarean section or other uterine surgery, pregestational or insulin dependent diabetes, hypertensive disorder of pregnancy, known oligohydramnios (amniotic fluid index < 50 mm or deepest vertical pocket < 20 mm), or small for gestational age fetus (estimated fetal weight ≤ 2 standard deviations according to the sex and gestational age specific to Swedish reference), diagnosed fetal anomaly, contraindication to vaginal birth, and any other maternal condition affecting the progress of the pregnancy to 42 weeks. Parity: 55% nulliparous State of cervix: mixed
Interventions	Induction group (n = 1381): labour induction at 41 weeks' gestation (early induction); randomisation was done between 40⁺⁶ weeks and 41⁺¹ weeks. Labour was induced within 24 hours of randomisation (same or next day). Expectant group (n = 1379): EM and induction at 42 weeks' gestation (late induction). Labour was induced at 42 weeks⁺⁰ to 42 weeks⁺¹. IOL was carried out in the same way in both groups: Amniotomy was performed if the fetal head was well engaged and the cervix was ripe (Bishop score ≥ 6 for primiparous women and ≥ 5 for multiparous women), followed by oxytocin infusion after 1‐2 hours without spontaneous regular contractions. If the fetal head was not engaged and the cervix was less ripe, any of the following methods was used according to local routines: mechanical dilation with a Foley‐like catheter, prostaglandin E1 (misoprostol, oral or vaginal), prostaglandin E2 (dinoprostone, vaginal).
Outcomes	Primary outcome: composite of stillbirth, neonatal death and neonatal morbidity (defined as at least 1 of the following variables: Apgar score < 7 at 5 minutes, metabolic acidosis defined as pH < 7.05 and base deficit > 12 mmol/L in umbilical artery or pH < 7.00 in umbilical artery, HIE I‐III, intracranial haemorrhage, neonatal convulsions, meconium aspiration syndrome, mechanical ventilation, obstetric brachial plexus injury) Mother: use of epidural anaesthesia, caesarean, operative vaginal birth, duration of labour (from onset of regular contractions to birth), chorioamnionitis, shoulder dystocia, third‐ or fourth‐degree perineal tear, postpartum haemorrhage (> 1000 mL), wound infection, urinary tract infection, endometritis, sepsis, and breastfeeding at discharge from hospital and at 4 weeks postpartum; cervical tear, uterine rupture, hypertensive disorders of pregnancy (pre‐eclampsia, gestational hypertension, eclampsia), venous thromboembolism, duration of stay in hospital, ICU admission, mortality with 42 days. Baby: components of composite; admission to NICU, Apgar score < 4 at 5 minutes, birthweight, macrosomia (≥ 4500 g), neonatal jaundice, therapeutic hypothermia, pneumonia, or sepsis: neonatal hypoglycaemia, birth trauma (fracture of long bone, clavicle or skull, other neurological injury, retinal haemorrhage, or facial nerve palsy), SGA and LGA.
Notes	Trial recruitment target was 10,000 but the study was stopped early due to a higher perinatal mortality rate in the EM group. Induction was carried out in the same way for both groups; monitoring was not performed routinely but further examinations were initiated for usual obstetric indication such as decreased fetal movements. All women in the Stockholm area were offered a routine ultrasound scan at 41 weeks prior to randomisation. Funding*: Swedish Government and county councils, Health Technology Centre at Sahlgrenska University Hospital, Foundation of the Health and Medical Care committee of the Region of Vastra Gotaland, Sweden, Hjalmar Svensson Foundation, Foundation Mary von Sydow, born Wijk donation fund, Uppsala‐Orebro regional research council, region Orebro County research committee, ALF agreement in Stockholm, Centre for Clinical Research Dalama‐Uppsala University, Sweden. The funders had no role in study design, data collection, data analysis, data interpretation, or writing of the report. The researchers were independent of the funders. All authors declared no support from any organisation for the submitted work; no financial relationship with any organisation that might have an interest in the submitted work in the previous three years, no other relationships or activities that could appear to have influenced the submitted work.
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Central online randomisation by dynamic allocation (actively minimises the imbalance between groups, by using centre and parity as variables)
Allocation concealment (selection bias)	Low risk	As above
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not feasible to blind women or staff
Blinding of outcome assessment (detection bias) All outcomes	High risk	Not feasible to blind women or staff
Incomplete outcome data (attrition bias) All outcomes	Low risk	2/1383 women in the intervention group withdrew consent before intervention.
Selective reporting (reporting bias)	Low risk	Protocol published; extensive range of outcomes reported (with individual components of composite reported separately)
Other bias	Low risk	Baseline characteristics similar

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Witter 1987.

*Study characteristics*
Methods	RCT
Participants	Number of women randomised: 200 Setting: Baltimore, USA Study date: not reported Inclusion criteria GA: 42 completed weeks (enrolled at 41 weeks, intervention at 42 weeks) Uncomplicated pregnancy Exclusion criteria No additional criteria reported State of cervix: not mentioned
Interventions	Induction group (n = 103): oxytocin infusion with AROM when possible versus EM group (n = 97): Estriol measurements 2‐3/week. In both groups women initiated fetal movement counting. If reduced fetal movements, FHR and estriol testing were undertaken at 41 completed weeks.
Outcomes	Mother: GA at birth; length of hospital stay; urinary estriol/creatinine ratio; maternal complications; endometritis; pre‐eclampsia; PROM; caesarean section + indications Baby: birthweight; biparietal diameter; placental weight; Dubowitz score (assesses infant GA); SGA/AGA/LGA; fetal distress; meconium staining; infant complications; Apgar scores (< 7 at 5 minutes); fetal anomalies; post‐mature infants; meconium aspiration
Notes	Funding: not reported Declarations of interest: not reported
*Risk of bias*
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The randomisation sequence was generated using a computer‐generated random number table.
Allocation concealment (selection bias)	Unclear risk	Allocation concealment was achieved using sequentially labelled sealed envelopes, but there was no mention of opaqueness.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Appeared that blinding was not feasible
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinded outcome assessment was not mentioned.
Incomplete outcome data (attrition bias) All outcomes	Low risk	3/103 women and 2/97 women in the induction and EM groups dropped out of the study; 35/103 women and 39/97 in the induction and EM groups birthing prior to 42 completed weeks (and were included); all were included in the analyses.
Selective reporting (reporting bias)	Unclear risk	No detailed outcomes were prespecified in the methods; perinatal death was not reported. No access to trial protocol to further assess selective reporting
Other bias	Low risk	Appeared to be free of other bias

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^AGA:^{appropriate for gestational age; AROM: artificial rupture of membranes/amniotomy; CTG: cardiotocography; EBL: estimated blood loss; EFW: estimation of fetal weight; EM: expectant management; FHR: fetal heart rate; GA: gestational age; HIE: hypoxic ischaemic encelopathy;  HIV: human immunodeficiency virus; IOL: induction of labour; IND: induction; ITT: intention to treat; IU: international units; IUFD: intrauterine fetal death IUGR: intrauterine fetal growth restriction  IV: intravenous; IVF: in‐vitro fertilisation; LGA: large‐for‐gestational age; LMP: last menstrual period mIU: milli‐international units; mU: milli‐units; NICU: neonatal intensive care unit; NST: nonstress test; PGE2 (and PE2): prostaglandin E2; PROM: premature rupture of membranes; RCT: randomised controlled trial; ROM: rupture of membranes; SGA: small‐for‐gestational age}

Characteristics of excluded studies [ordered by study ID]

Study	Reason for exclusion
Alcalay 1996	PROM at term
Amano 1999	Alternate allocation trial
Ascher‐Walsh 2000	Compared 2 forms of IOL
Bell 1993	Trial of cervical ripening not IOL
Berghella 1996	Membrane stripping to decrease the need for formal IOL
Boulvain 1998	Membrane stripping to decrease the need for formal IOL
Buttino 1990	Trial of cervical ripening not IOL
Cardozo 1986	Alternate allocation trial
Conway 2000	Trial of active versus expectant management in women with oligohydramnios
CTRI/2018/09/015719	High‐risk pregnancy (women with previous caesarean) included in this trial
Damania 1992	Trial of cervical ripening (2 methods) not IOL
Dare 2002	Trial of cervical ripening not IOL
De Aquino 2003	Compares 2 forms of IOL
Doany 1997	Trial of cervical ripening not IOL
Dunn 1989	Intervention not a policy to induce labour compared with expectant management
El‐Torkey 1992	Trial of cervical ripening not IOL
Elliott 1984	Trial of nipple stimulation as a method of cervical ripening. No commitment to delivery within a given time or protocol
Evans 1983	Compares 2 forms of IOL
Frass 2011	Trial where all women were judged to be at risk (severe pre‐eclampsia)
Garry 2000	Alternate allocation trial
Giacalone 1998	Trial of cervical ripening not IOL
Gregson 2015	Assessing effectiveness of acupuncture for IOL (role of acupuncture not established)
Hage 1993	Trial of cervical ripening not IOL
Heden 1991	Alternate allocation trial
Hernandez‐Castro 2008	Not a RCT
Imsuwan 1999	This is a RCT evaluating the effectiveness of weekly membrane sweeping in labour initiation for women at 41 completed weeks. It is not evaluating a policy of stopping the pregnancy at 41 weeks
Ingemarsson 1987	Trial of cervical ripening not IOL
Iqbal 2004	Alternate allocation trial
Jenssen 1977	Trial of cervical ripening not IOL
Kadar 1990	Trial of nipple stimulation as a method of cervical ripening. No commitment to delivery within a given time or protocol
Katz 1983	Alternate allocation trial
Kipikasa 2005	Comparing alternate methods for IOL
Klopper 1969	Trial of cervical ripening not IOL
Knox 1979	Quasi‐randomised (last digit of hospital number)
Lee 1997	Compares 2 forms of IOL
Lemancewicz 1999	Compares 2 forms of IOL
Lien 1998	Trial of cervical ripening not IOL
Lyons 2001	Trial of cervical ripening not IOL
Magann 1998	Trial of cervical ripening not IOL
Magann 1999	Compares 2 forms of IOL
Mancuso 1998	Compares 2 forms of IOL
Meydanli 2003	Compares 2 forms of IOL
Misra 1994	Compares 2 forms of IOL
Müller 1995	Compares 2 forms of IOL
Neri 2014	Assessing effectiveness of acupressure for IOL (role of acupuressure not established)
Newman 1997	Trial of cervical ripening not IOL
Nicholson 2008	Trial where all women were judged to be at risk
Ohel 1996	Alternate allocation
PACTR201805002872322	Not low risk pregnancies
Papageorgiou 1992	Compared 2 forms of IOL
Paul 1988	Protocol for RCT only ‐ no results
Rayburn 1988	Trial of cervical ripening not IOL
Rayburn 1999	Trial of cervical ripening not IOL
Rijnders 2011	Compared 2 alternative management strategies for IOL
Roberts 1986	Trial of cervical ripening not IOL
Satin 1991	Compared 2 forms of IOL
Sawai 1991	Trial of cervical ripening not IOL
Sawai 1994	Trial of cervical ripening not IOL
Stenlund 1999	Mifepristone versus placebo for IOL, but all women given PGE2 if necessary after 48 hours
Su 1996	Both groups induced within 2 days with alternative methods
Surbek 1997	Compared 2 forms of IOL
Suzuki 1999	Immediate IOL versus expectant management in twin pregnancies
Williams 1990	Trial of cervical ripening not IOL
Wing 2000	Trial of cervical ripening not IOL
Wong 2002	Trial of cervical ripening not IOL
Ziaei 2003	Trial of cervical ripening not IOL

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IOL: induction of labour PGE2: prostaglandin E2 PROM: premature rupture of membranes RCT: randomised controlled trial

Characteristics of studies awaiting classification [ordered by study ID]

Benito Reyes 2010.

Methods	Quote: "prospective study"
Participants	200
Interventions	Elective induction versus expectant management
Outcomes	Caesarean section
Notes

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ISRCTN74323479.

Methods	RCT (ISRCTN74323479)
Participants	100 pregnant primiparous women who have not laboured at or beyond 41 weeks' gestation with cervical length > 3 cm
Interventions	Mifepristone versus standard care
Outcomes	Length of time from induction to onset of labour
Notes

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Characteristics of ongoing studies [ordered by study ID]

ISRCTN15646866.

Study name	Induction of labour at 39 weeks or beyond in multiparous women with a favourable cervix (ISRCTN15646866)
Methods	RCT
Participants	160 pregnant women ≥ 39 weeks' gestation, with at least 1 previous vaginal birth
Interventions	1) induction of labour at 39 weeks 2) expectant management with recommendation to induce at 41 weeks if woman has not given birth
Outcomes	Time of giving birth; maternal satisfaction
Starting date	30 September 2016
Contact information	Dr Aida Othman, Dept Obstetrics & Gynaecology, University Malaya Medical Centre, Kuala Lumpur, 59100, Malaysia
Notes

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ISRCTN83219789.

Study name	The Finnish randomised controlled multicentre trial on optimal timing of labor induction in nulliparous women with post‐term pregnancy (ISRCTN83219789)
Methods	RCT
Participants	Nulliparous pregnant women (n = 600)
Interventions	1) induction at 41 + 0 weeks 2) induction at 41 + 5 to 42 + 1 weeks, according to hospital policy
Outcomes	Caesarean section
Starting date	March 2018
Contact information	Associate Professor Leena Rahkonen, Department of Obstetrics and Gynecology, Helsinki University Hospital, Haartmaninkatu 2, Helsinki 00029 HUS, Finland Tel: +358 504 271248, E‐mail: leena.rahkonen@hus.fi
Notes

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^CPAP:^{continuous positive airway pressure GW: gestational weeks HIE: Hypoxic ischaemic encephalopathy IVH: intraventricular haemorrhage RCT: Randomised controlled trial}

Differences between protocol and review

2020 update of the review

The title has been changed to 'Induction of labour at or beyond 37 weeks' gestation' to reflect increasing debate about how 'term' should be defined.
The subgroup analyses by gestational age are now reported by induction at < 40 weeks; 40 to 41 weeks; and > 41 weeks.
We have included an additional subgroup analysis based on parity.

2018 update of the review

We have updated the methods in line with those in the standard template used by Cochrane Pregnancy and Childbirth.
We have omitted the outcome of vaginal birth as it is the obverse of caesarean section.
We have used the GRADE approach to assess the quality of the body of evidence and we have included ’Summary of findings’ tables.
We have added three new infant secondary outcomes (birthweight; birthweight > 4000 g; neonatal trauma), which were reported as non‐prespecified, but important, outcomes in the previous version of this review, in our main outcomes list.
The secondary infant outcome 'Perinatal death (stillbirth, newborn deaths within first week)' (which is the same as the primary outcome) has been changed to two separate outcomes, 'Stillbirth' and 'Neonatal death within the first week'.
The subgroup analyses by gestational age are now reported by induction at < 41 weeks; and at ≥ 41 weeks.
We have added in an additional search of ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP).

In the previous (Gülmezoglu 2012) update of this review:

The subgroup analyses by gestational age were reported by induction at 39 to 40 weeks; at 41 weeks; and at > 41 weeks.
The methods were updated to reflect the latest Cochrane Handbook for Systematic Reviews of Interventions version (Higgins 2011).

Contributions of authors

For this updated review, Philippa Middleton (PM), Emily Shepherd (ES) and Judith Gomersall (JG) applied the selection criteria, extracted data for included studies, assessed risk of bias, carried out GRADE assessments and prepared SoF tables. All five authors (PM, ES, JG, Jonathan Morris, Caroline Crowther) contributed to drafting and editing of this update.

Sources of support

Internal sources

Robinson Research Institute, The University of Adelaide, Adelaide, Australia
Women and Kids, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia
Liggins Institute, The University of Auckland, Auckland, New Zealand

External sources

NHMRC: National Health and Medical Research Council, Australia

Funding for the Cochrane Pregnancy and Childbirth Australian and New Zealand Satellite
NIHR: National Institute for Health Research, UK

NIHR Cochrane Programme Grant Project: 13/89/05 – Pregnancy and childbirth systematic reviews to support clinical guidelines
UNDP‐UNFPA‐UNICEF‐WHO‐World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP), Department of Sexual and Reproductive Health and Research, World Health Organization, Switzerland

This review is supported by funding to Cochrane Pregnancy and Childbirth (University of Liverpool)

Declarations of interest

Philippa Middleton: none known.

Caroline A Crowther: none known.

Jonathan Morris: none known.

Emily Shepherd: none known.

Judith Gomersall: none known.

Edited (no change to conclusions)

References

References to studies included in this review

Augensen 1987 {published data only}

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Baev 2017 {published data only}

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Chanrachkul 2003 {published data only}

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Cole 1975 {published data only}

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Egarter 1989 {published data only}

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Hannah 1992 {published data only}

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Henry 1969 {published data only}

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Martin 1978 {published data only}

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NICHHD 1994 {published data only}

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ISRCTN11517275. Induction of labour versus expectant management for women over 35 years. isrctn.com/ISRCTN11517275 (first received 23 August 2012).
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Elden H, Hagberg H, Wessberg A, Sengpiel V, Herbst A, Bullarbo M, et al. Study protocol of SWEPIS a Swedish multicentre register based randomised controlled trial to compare induction of labour at 41 completed gestational weeks versus expectant management and induction at 42 completed gestational weeks. BMC Pregnancy and Childbirth 2016;16:49. [DOI] [PMC free article] [PubMed] [Google Scholar]
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References to ongoing studies

ISRCTN15646866 {published data only}ISRCTN15646866

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ISRCTN83219789. The Finnish randomised controlled multicentre trial on optimal timing of labor induction in nulliparous women with post-term pregnancy. www.isrctn.com/ISRCTN83219789 (first received 20 July 2017).

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PERMALINK

Induction of labour at or beyond 37 weeks' gestation

Philippa Middleton

Emily Shepherd

Jonathan Morris

Caroline A Crowther

Judith C Gomersall

Abstract

Background

Objectives

Search methods

Selection criteria

Data collection and analysis

Main results

Authors' conclusions

Plain language summary

Summary of findings

Summary of findings 1. Labour induction versus expectant management (infant/child outcomes).

5. Causes of death (stillbirths and livebirth deaths).

Summary of findings 2. Labour induction versus expectant management (maternal outcomes).

Background

Description of the condition

Description of the intervention

How the intervention might work

Why it is important to do this review

Objectives

Methods

Criteria for considering studies for this review

Types of studies

Types of participants

Types of interventions

Types of outcome measures

Primary outcomes

Secondary outcomes

For the infant/child

For the mother

Health services use

Search methods for identification of studies

Electronic searches

Searching other resources

Data collection and analysis

Selection of studies

Data extraction and management

Assessment of risk of bias in included studies

(1) Allocation (checking for possible selection bias)

(2) Allocation concealment (checking for possible selection bias)

(3.1) Blinding of participants and personnel (checking for possible performance bias)

(3.2) Blinding of outcome assessment (checking for possible detection bias)

(4) Incomplete outcome data (checking for possible attrition bias due to the amount, nature and handling of incomplete outcome data)

(5) Selective reporting (checking for reporting bias)

(6) Other bias (checking for bias due to problems not covered by (1) to (5) above)

(7) Overall risk of bias

Measures of treatment effect

Dichotomous data

Continuous data

Unit of analysis issues

Cluster‐randomised trials

Cross‐over trials

Multiple pregnancies

Multi‐armed trials

Dealing with missing data

Assessment of heterogeneity

Assessment of reporting biases

Data synthesis

Subgroup analysis and investigation of heterogeneity

For the infant/child

For the mother

Sensitivity analysis

For the infant/child

For the mother

Assessment of the certainty of the evidence using the GRADE approach

For the infant/child

For the mother

Results

Description of studies

Results of the search

1.

Included studies

Settings

Date trials published/conducted