Breast stimulation for cervical ripening and induction of labour

Abstract

Background

Breast stimulation has been suggested as a means of inducing labour. It is a non‐medical intervention allowing women greater control over the induction process. This is one of a series of reviews of methods of cervical ripening and labour induction using a standardised methodology.

Objectives

To determine the effectiveness of breast stimulation for third trimester cervical ripening or induction of labour in comparison with placebo/no intervention or other methods of induction of labour.

Search methods

The Cochrane Pregnancy and Childbirth Group's Trials Register (15 September 2009) and bibliographies of relevant papers.

Selection criteria

Clinical trials of breast stimulation for third trimester cervical ripening or labour induction.

Data collection and analysis

A strategy was developed to deal with the large volume and complexity of trial data relating to labour induction. This involved a two‐stage method of data extraction.

Main results

Six trials (719 women) were included.

Analysis of trials comparing breast stimulation with no intervention found a significant reduction in the number of women not in labour at 72 hours (62.7% versus 93.6%, relative risk (RR) 0.67, 95% confidence interval (CI) 0.60 to 0.74). This result was not significant in women with an unfavourable cervix. A major reduction in the rate of postpartum haemorrhage was reported (0.7% versus 6%, RR 0.16, 95% CI 0.03 to 0.87). No significant difference was detected in the caesarean section rate (9% versus 10%, RR 0.90, 95% CI 0.38 to 2.12) or rates of meconium staining. There were no instances of uterine hyperstimulation. Three perinatal deaths were reported (1.8% versus 0%, RR 8.17, 95% CI 0.45 to 147.77).

When comparing breast stimulation with oxytocin alone the analysis found no difference in caesarean section rates (28% versus 47%, RR 0.60, 95% CI 0.31 to 1.18). No difference was detected in the number of women not in labour after 72 hours (58.8% versus 25%, RR 2.35, 95% CI 1.00 to 5.54) or rates of meconium staining. There were four perinatal deaths (17.6% versus 5%, RR 3.53, 95% CI 0.40 to 30.88).

Authors' conclusions

Breast stimulation appears beneficial in relation to the number of women not in labour after 72 hours, and reduced postpartum haemorrhage rates. Until safety issues have been fully evaluated it should not be used in high‐risk women. Further research is required to evaluate its safety, and should seek data on postpartum haemorrhage rates, number of women not in labour at 72 hours and maternal satisfaction.

Plain language summary

Breast stimulation for cervical ripening and induction of labour

Breast stimulation appears beneficial in relation to the number of women not in labour after 72 hours, and reduced postpartum haemorrhage rates.

Breast stimulation causes the womb to contract, though the mechanism remains unclear. It may increase levels of the hormone oxytocin, which stimulates contractions. It is a non‐medical method allowing the woman greater control over the process of attempting to induce labour. The review of six trials (719 women) found insufficient research to evaluate the safety of breast stimulation in a high‐risk population and until safety issues have been fully evaluated, it should not be considered for use in this group.

Background

Sometimes it is necessary to bring on labour artificially because of safety concerns for the mother or baby. This review is one of a series of reviews of methods of labour induction using a standardised protocol. For more detail on the rationale for this methodological approach, please refer to the currently published generic protocol (Hofmeyr 2009). The generic protocol describes how a number of standardised reviews will be combined to compare various methods of preparing the cervix of the uterus and inducing labour.

Breast stimulation as a means of labour induction allows women greater control over the induction process and has the advantage of being a natural and inexpensive non‐medical method. Observational data have demonstrated a link between stimulation of both breasts (bilateral stimulation) and uterine hyperstimulation (Lenke 1984). As a result of observed uterine hyperstimulation randomised controlled trials have studied breast massage or nipple stimulation of one breast at a time (unilateral stimulation). Breast stimulation has historically been used to induce and augment labour in many different cultures. European medical texts of the 18th and 19th century report on its use for the management of protracted labour (Curtis 1999). Whilst the actual mechanism by which breast stimulation results in cervical changes is not known, it is known to cause uterine contractions, and has been recommended for contraction stress tests (Huddleston 1984). It has been suggested that breast stimulation results in the production of endogenous oxytocin in both pregnant and non‐pregnant women (Amico 1986; Christensson 1989), however no direct relationship between oxytocin levels and intrapartum uterine response to breast stimulation has been clearly demonstrated (Christensson 1989; Seoud 1993).

Objectives

To determine from the best available evidence, the effectiveness and safety of breast stimulation for third trimester cervical ripening and induction of labour in comparison with placebo/no intervention or other methods of induction of labour.

Methods

Criteria for considering studies for this review

Types of studies

Clinical trials comparing breast stimulation for cervical ripening or labour induction, with placebo/no treatment or other methods listed above it on a predefined list of methods of labour induction (see 'Methods of the review'); the trials included some form of random allocation to either group; and they reported one or more of the prestated outcomes.

Types of participants

Pregnant women due for third trimester induction of labour, carrying a viable fetus.

Predefined subgroup analyses were (see list below): previous caesarean section or not; nulliparity or multiparity; membranes intact or ruptured, and cervix unfavourable, favourable or undefined. Only those outcomes with data appear in the analysis tables.

Types of interventions

Breast stimulation either by self stimulation through massage or by a mechanical method compared with placebo/no treatment or any other method above it on a predefined list of methods of labour induction.

Types of outcome measures

Clinically relevant outcomes for trials of methods of cervical ripening/labour induction have been prespecified by two authors of labour induction reviews (Justus Hofmeyr and Zarko Alfirevic). Differences were settled by discussion.

Five primary outcomes were chosen as being most representative of the clinically important measures of effectiveness and complications. Subgroup analyses were limited to the primary outcomes: 
 (1) vaginal delivery not achieved within 24 hours; 
 (2) uterine hyperstimulation with fetal heart rate (FHR) changes; 
 (3) caesarean section; 
 (4) serious neonatal morbidity or perinatal death (e.g. seizures, birth asphyxia defined by trialists, neonatal encephalopathy, disability in childhood); 
 (5) serious maternal morbidity or death (e.g. uterine rupture, admission to intensive care unit, septicaemia).

Perinatal and maternal morbidity and mortality are composite outcomes. This is not an ideal solution because some components are clearly less severe than others. It is possible for one intervention to cause more deaths but less severe morbidity. However, in the context of labour induction at term this was unlikely. Composite outcomes also provide heightened sensitivity to a change in the incidence of these rare events. The incidence of individual components was explored as secondary outcomes (see below).

Secondary outcomes relate to measures of effectiveness, complications and satisfaction.

Measures of effectiveness: 
 (6) cervix unfavourable/unchanged after 12 to 24 hours; 
 (7) oxytocin augmentation.

Complications: 
 (8) uterine hyperstimulation without FHR changes; 
 (9) uterine rupture; 
 (10) epidural analgesia; 
 (11) instrumental vaginal delivery; 
 (12) meconium stained liquor; 
 13) Apgar score less than seven at five minutes; 
 (14) neonatal intensive care unit admission; 
 (15) neonatal encephalopathy; 
 (16) perinatal death; 
 (17) disability in childhood; 
 (18) maternal side‐effects (all); 
 (19) maternal nausea; 
 (20) maternal vomiting; 
 (21) maternal diarrhoea; 
 (22) other maternal side‐effects; 
 (23) postpartum haemorrhage (as defined by the trial authors); 
 (24) serious maternal complications (e.g. intensive care unit admission, septicaemia but excluding uterine rupture); 
 (25) maternal death.

Measures of satisfaction: 
 (26) woman not satisfied; 
 (27) caregiver not satisfied.

While all the above outcomes were sought, only those with data appear in the analysis tables.

The terminology of uterine hyperstimulation is problematic (Curtis 1999). In the reviews we used the term 'uterine hyperstimulation without FHR changes' to include uterine tachysystole (more than five contractions per 10 minutes for at least 20 minutes) and uterine hypersystole/hypertonus (a contraction lasting at least two minutes) and 'uterine hyperstimulation with FHR changes' to denote uterine hyperstimulation syndrome (tachysystole or hypersystole with FHR changes such as persistent decelerations, tachycardia or decreased short‐term variability).

Outcomes were included in the analysis if reasonable measures were taken to minimise observer bias; and data were available for analysis according to original allocation.

Search methods for identification of studies

Electronic searches

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register by contacting the Trials Search Co‐ordinator (15 September 2009).

The Cochrane Pregnancy and Childbirth Group's Trials Register is maintained by the Trials Search Co‐ordinator and contains trials identified from:

1. quarterly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);

2. monthly searches of MEDLINE;

3. handsearches of 30 journals and the proceedings of major conferences;

4. weekly current awareness search of a further 36 journals plus monthly BioMed Central email alerts.

Details of the search strategies for CENTRAL and MEDLINE, the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service can be found in the 'Search strategies for identification of studies' section within the editorial information about the Cochrane Pregnancy and Childbirth Group.

Trials identified through the searching activities described above are given a code (or codes) depending on the topic. The codes are linked to review topics. The Trials Search Co‐ordinator searches the register for each review using these codes rather than keywords.

The search was performed simultaneously for all reviews of methods of inducing labour, as outlined in the generic protocol for these reviews (Hofmeyr 2009).

The reference lists of trial reports and reviews were searched by hand.

We did not apply any language restrictions.

Searching other resources

We searched the reference lists of trial reports and reviews by hand.

We did not apply any language restrictions.

Data collection and analysis

A strategy was developed to deal with the large volume and complexity of trial data relating to labour induction. Many methods have been studied, in many different groups of women undergoing labour induction. Most trials are intervention‐driven, comparing two or more methods in various categories of women.

To avoid duplication of data in these reviews, the labour induction methods have been listed in a specific order, from one to 27. Each primary review included comparisons between one of the methods (from two to 27) with only those methods above it on the list. Thus, the review of intravenous oxytocin (4) will include only comparisons with intracervical prostaglandins (3), vaginal prostaglandins (2), or placebo (1). Methods identified in the future will be added to the end of the list. The current list is as follows:

1. placebo/no treatment;

2. vaginal prostaglandins (Kelly 2003);

3. intracervical prostaglandins (Boulvain 2008);

4. intravenous oxytocin (Kelly 2001a);

5. amniotomy (Bricker 2000);

6. intravenous oxytocin with amniotomy (Howarth 2001);

7. vaginal misoprostol (Hofmeyr 2003);

8. oral misoprostol (Alfirevic 2006);

9. mechanical methods including extra‐amniotic Foley catheter (Boulvain 2001);

10. membrane sweeping (Boulvain 2005);

11. extra‐amniotic prostaglandins (Hutton 2001);

12. intravenous prostaglandins (Luckas 2000);

13. oral prostaglandins (French 2001);

14. mifepristone (Hapangama 2009);

15. oestrogens with or without amniotomy (Thomas 2001);

16. corticosteroids (Kavanagh 2006a);

17. relaxin (Kelly 2001b);

18. hyaluronidase (Kavanagh 2006b);

19. castor oil, bath or enema, or both (Kelly 2001c);

20. acupuncture (Smith 2004);

21. breast stimulation;

22. sexual intercourse (Kavanagh 2001);

23. homeopathic methods (Smith 2003);

24. nitric oxide (Kelly 2008);

25. buccal or sublingual misoprostol (Muzonzini 2004);

26. hypnosis;

27. other methods for induction of labour.

The primary reviews will be analysed by the following subgroups:

1. previous caesarean section or not;

2. nulliparity or multiparity;

3. membranes intact or ruptured;

4. cervix favourable, unfavourable or undefined.

The trials included in the review were extracted from an initial set of trials covering all interventions used in induction of labour (see above for details of search strategy). The data extraction process was conducted centrally. This was co‐ordinated from the Clinical Effectiveness Support Unit (CESU) at the Royal College of Obstetricians and Gynaecologists, UK, in co‐operation with the Pregnancy and Childbirth Group of The Cochrane Collaboration. This process allowed the data extraction process to be standardised across all the reviews.

The trials were initially reviewed on eligibility criteria, using a standardised form and the basic selection criteria specified above. Following this, data were extracted to a standardised data extraction form which was piloted for consistency and completeness. The pilot process involved the researchers at the CESU and previous review authors in the area of induction of labour.

Information was extracted regarding the methodological quality of trials on a number of levels. This process was completed without consideration of trial results. Assessment of selection bias examined the process involved in the generation of the random sequence and the method of allocation concealment separately. These were then judged as adequate or inadequate using the criteria described in Appendix 1 for the purpose of the reviews.

We examined performance bias with regard to whom was blinded in the trials i.e. participant, caregiver, outcome assessor or analyst. In many trials the caregiver, assessor and analyst were the same party. We sought details of the feasibility and appropriateness of blinding at all levels.

Individual outcome data were included in the analysis if they meet the prestated criteria in 'Types of outcome measures'. Included trial data were processed as described in the Cochrane Reviewers' Handbook (Clarke 2000). Data extracted from the trials were analysed on an intention‐to‐treat basis (when this was not done in the original report, re‐analysis is performed if possible). Where data were missing, clarification was sought from the original authors. If the attrition was such that it might significantly affect the results, these data were excluded from the analysis. This decision rested with the authors of primary reviews and is clearly documented. If missing data become available, they will be included in the analyses.

We extracted data from all eligible trials to examine how issues of quality influence effect size in a sensitivity analysis. In trials where reporting was poor, methodological issues were reported as unclear or clarification sought.

Due to the large number of trials, double data extraction was not feasible and agreement between the three data extractors was therefore assessed on a random sample of trials.

Once the data had been extracted, they were distributed to individual authors for entry onto the Review Manager computer software (RevMan 2000), checked for accuracy, and analysed as above using the Review Manager software. For dichotomous data, relative risks and 95% confidence intervals were calculated, and in the absence of heterogeneity, results were pooled using a fixed‐effect model.

The predefined criteria for sensitivity analysis included all aspects of quality assessment as mentioned above, including aspects of selection, performance and attrition bias.

Primary analysis was limited to the prespecified outcomes and subgroup analyses. In the event of differences in unspecified outcomes or subgroups being found, these were analysed post hoc, but clearly identified as such to avoid drawing unjustified conclusions.

Results

Description of studies

In total 13 studies were considered, seven were excluded, and six included, examining a total of 719 women. For further details of study characteristics refer to 'Characteristics of included studies and Characteristics of excluded studies.

Two separate studies were reported in the same paper (Adewole 1993a; Adewole 1993b). One study was a three‐armed trial, breast stimulation versus oxytocin versus no intervention (Damania 1992). Only one trial considered breast stimulation by breast pump (Chayen 1986). In all studies gentle breast and nipple stimulation was performed by the women, who were all instructed to stimulate only one breast at a time.

Five included studies compared breast stimulation to placebo/no intervention (Adewole 1993a; Adewole 1993b; Damania 1992; Elliott 1984a; Salmon 1986a).

• In two trials stimulation was performed for one hour per day for three days. Both trials were set in a Nigerian hospital including only women at term; neither specified whether they were high or low risk. One included only primiparous women (Adewole 1993a), the other only multiparous women (Adewole 1993b).

• In the three other studies breast stimulation was performed for three hours per day. One of these studies set in an Indian hospital was of high‐risk primiparous women at term who were instructed to perform stimulation for one hour, three times per day, alternating breasts every 10 minutes (Damania 1992). One Singapore study included only low‐risk, primiparous women. After an initial session of stimulation at the hospital they were instructed to perform breast stimulation for three hours per day, over two or three sessions at home (Salmon 1986a). One American study also instructed women to perform breast stimulation at home, only low‐risk women were included (parity was not stated), stimulation was for one hour three times per day, alternating breasts every 15 minutes (Elliott 1984a).

Two included studies compared breast stimulation to oxytocin alone (Chayen 1986; Damania 1992).

• One of these studies described above was of high‐risk primiparous women at term who were instructed to perform stimulation for one hour, three times per day, alternating breasts every 10 minutes (Damania 1992).

• One American study compared oxytocin with breast stimulation by breast pump (Chayen 1986). Any woman admitted to the labour suite for induction was eligible to participate, no other eligibility criteria were stated. Stimulation was by breast pump set at 'normal' (250 mm Hg of negative pressure). The nurse attending the woman alternated the pump every 15 minutes, until uterine contractions were greater or equal to 200 Montevideo units. Contractions were maintained at three minute intervals either by reducing the negative pressure or switching the pump off.

Excluded studies

Two studies of breast stimulation versus no intervention were excluded because they were cross‐over trials (Adewole 1993c; Salmon 1986b). One trial of breast stimulation versus no intervention was excluded, as it randomised the control group a second time (Elliott 1984b). Three trials were excluded because they did not report any of the prespecified outcomes (Di Lieto 1989; Elliott 1983; Kadar 1990). One controlled trial was excluded because it was not randomised (Damania 1988).

Risk of bias in included studies

Randomisation

Four studies used random‐number tables (Adewole 1993a; Adewole 1993b; Elliott 1984a; Salmon 1986a). One study randomised by case record number (Chayen 1986). The method of randomisation was not stated in one study (Damania 1992).

Concealment

Allocation concealment was unclear in five of the studies, and due to randomisation by case record number was inadequate in one (Chayen 1986).

Blinding

Double blinding was not feasible in the included studies. In three studies the outcome assessor was blinded to intervention (Adewole 1993a; Adewole 1993b; Salmon 1986a). It was not stated if the analyst was blinded in any of the trials.

Missing data

One trial was stopped after four perinatal deaths (Damania 1992). It was a three‐armed trial with 20 women randomised to each arm (breast stimulation versus oxytocin versus no intervention). Three deaths occurred in the breast stimulation arm and one in the oxytocin arm. The study was stopped with only 17 women having entered the breast stimulation arm. No outcome data were presented for the three missing women, all women remained in the groups to which they were randomised and the analysis was conducted on an available case basis.

Effects of interventions

All the outcomes listed under 'Types of outcome measures' and subgroups defined in 'Types of participants', were sought. Only those with data appear in the analysis tables.

Data discussed applies to the 'all women' group and unless stated there was no difference between any of the prespecified subgroups.

Breast stimulation versus no intervention: five studies (n = 637)

Prespecified outcomes

When trials comparing breast stimulation with no intervention were analysed there was little difference in caesarean section rates (9% versus 10%, relative risk (RR) 0.90, 95% confidence interval (CI) 0.38 to 2.12). Only one trial (n = 200) reported this outcome (Elliott 1984a). There were no instances of uterine hyperstimulation in any of the five studies. There was no discernible difference in the number of women who had an unfavourable/unchanged cervix after 12 to 24 hours (0% versus 5%, RR 0.39, 95% CI 0.02 to 8.97). Only one of the five trials (n = 37) reported this outcome (Damania 1992). There were three perinatal deaths all of which were in the breast stimulation arm of one trial (1.8% versus 0%, RR 8.17, 95% CI 0.45 to 147.76) (Damania 1992). This outcome was reported in three trials (n = 337) (Damania 1992; Elliott 1984a; Salmon 1986a). There was a small statistically non‐significant reduction in the rates of meconium staining (25.6% versus 30%, RR 0.85, 95% CI 0.56 to 1.28). Two trials (n = 237) reported this outcome (Damania 1992; Elliott 1984a).

There was a reduction in the rate of postpartum haemorrhage when breast stimulation was compared with no treatment (0.7% versus 6%, RR 0.16, 95% CI 0.03 to 0.87). This outcome was reported in two trials (n = 300) conducted by the same trialists (Adewole 1993a; Adewole 1993b).

Non‐prespecified outcomes

There was a reduction in the number of women not in labour after 72 hours in women who had used breast stimulation when compared with no treatment (62.7% versus 93.6%, RR 0.67, 95% CI 0.60 to 0.74). Four trials (n = 437) reported this outcome (Adewole 1993a; Adewole 1993b; Damania 1992; Salmon 1986a). This reduction remained significant when primiparous women and multiparous women were analysed separately, but did not remain significant in the one study that reported on this outcome in women with an unfavourable cervix. However, the relative risk estimates between the subgroups remained very similar (between 0.64 and 0.74). It is possible, therefore, that the non‐significant result is due to the smaller sample size available in subgroup analyses rather than the intervention's effect being really different between the groups.

Breast stimulation versus oxytocin alone: two studies (n = 99)

Prespecified outcomes

When trials comparing breast stimulation with oxytocin were analysed there was a difference in caesarean section rates. This was not statistically significant, however, due to the small sample sizes (28% versus 47%, RR 0.60, 95% CI 0.31 to 1.18). Only one trial (n = 62) reported this outcome (Chayen 1986). There were no instances of uterine hyperstimulation in either of the two trials. The difference in the number of women who had an unfavourable/unchanged cervix after 12 to 24 hours was not statistically significant (0% versus 20%, RR 0.13, 95% CI 0.01 to 2.25). This outcome was reported by only one trial (n = 37) (Damania 1992). There were a total of four perinatal deaths in one trial (n = 37), three were in the breast stimulation arm and one in the oxytocin arm (17.6% versus 5%, RR 3.53, 95% CI 0.40 to 30.88) (Damania 1992). The difference in the one trial (n = 37) which reported rates of meconium staining was not statistically significant (29.4% versus 20%, RR 1.47, 95% CI 0.47 to 4.62) (Damania 1992).

Non‐prespecified outcomes

When breast stimulation was compared with oxytocin alone the difference in the number of women not in labour after 72 hours was not statistically significant (58.8% versus 25%, RR 2.35, 95% CI 1.00 to 5.54). Only one trial (n = 37) reported this outcome (Damania 1992).

Discussion

None of the included studies reported on vaginal delivery not achieved within 24 hours, however there was a significant reduction in women not in labour after 72 hours in the breast stimulation group compared with the no intervention group. There were no instances of uterine hyperstimulation in any of the groups and a significant reduction in postpartum haemorrhage (breast stimulation compared with no intervention). Differences in caesarean section rates between breast stimulation and no intervention or oxytocin alone remained statistically non‐significant across comparisons. In comparison to no intervention or to oxytocin, no women in a breast stimulation arm had an unfavourable/unchanged cervix after 24 hours, though this finding did not reach significance. None of the trials reported upon women's satisfaction with treatment received.

Whilst breast stimulation would seem to work in that there was a significant reduction in the number of women not in labour after 72 hours and postpartum haemorrhage, this has to be considered against a background of increased perinatal mortality. All four instances of perinatal mortality were in the (Damania 1992) trial which was the only included trial specifically conducted on a high‐risk population. Of the deaths that occurred three were in the breast stimulation group and one in the oxytocin group. Of 57 women included in the trial, the indications for induction of labour were: post‐term pregnancy (n = 25); hypertension in pregnancy (n = 22); and intrauterine growth retardation (n = 10). The authors reported that a postmortem on one of the babies revealed no anomalies, no information was presented on the other three babies who died. The results of this study should be viewed with caution as it is the only included trial which did not clearly report method of randomisation, and there were three losses to follow up, which were not analysed on an intention‐to‐treat basis. The study was stopped due to perinatal deaths after only 17 of 20 women who had been randomised to the breast stimulation arm had entered the trial.

There are valid reasons not to use breast stimulation in a high‐risk population until safety issues have been evaluated further. However, this form of care is likely to be beneficial in a low‐risk population. The 84% reduction in postpartum haemorrhage, seen in the breast stimulation arms of two trials including 300 women, may be of particular interest to women and their healthcare providers in developing countries. Approximately 600,000 annual maternal deaths occur globally, the overwhelming majority in developing countries. It has been estimated that the single most common cause is severe bleeding, generally occurring postpartum and accounting for approximately 25% of maternal deaths (WHO 1999). This promising finding warrants further research.

Authors' conclusions

Implications for practice.

Breast stimulation appears beneficial in terms of a reduction in the number of women not in labour after 72 hours, and a reduction in postpartum haemorrhage. Until safety issues have been fully evaluated it should not be considered for use in a high‐risk population.

Implications for research.

Further randomised controlled trials on breast stimulation versus placebo/no intervention or other interventions for inducing labour should be undertaken to evaluate its efficacy and safety. Future trials should seek data on postpartum haemorrhage rates, the number of women not in labour at 72 hours and maternal satisfaction with the intervention.

What's new

Date	Event	Description
15 September 2009	New search has been performed	Search updated. No new reports identified.

History

Protocol first published: Issue 2, 2000
 Review first published: Issue 4, 2001

Date	Event	Description
24 April 2008	Amended	Converted to new review format.
10 March 2005	New citation required and conclusions have changed	Substantive amendment

Appendices

Appendix 1. Methodological quality of included studies

Methodological item	Adequate	Inadequate
Generation of random sequence	Computer‐generated sequence, random‐number tables, lot drawing, coin tossing, shuffling cards, throwing dice.	Case number, date of birth, date of admission, alternation.
Concealment of allocation	Central randomisation, coded drug boxes, sequentially sealed opaque envelopes.	Open allocation sequence, any procedure based on inadequate generation.

Data and analyses

Comparison 1. Breast stimulation versus no intervention (all women).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2 Uterine hyperstimulation with fetal heart rate changes	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
3 Caesarean section	1	200	Risk Ratio (M‐H, Fixed, 95% CI)	0.9 [0.38, 2.12]
4 Serious neonatal morbidity/perinatal death	3	337	Risk Ratio (M‐H, Fixed, 95% CI)	8.17 [0.45, 147.76]
6 Cervix unfavourable/unchanged after 12‐24 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	0.39 [0.02, 8.97]
8 Uterine hyperstimulation without fetal heart rate changes	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
12 Meconium stained liquor	2	237	Risk Ratio (M‐H, Fixed, 95% CI)	0.85 [0.56, 1.28]
13 Apgar score < 7 at 5 minutes	1	200	Risk Ratio (M‐H, Fixed, 95% CI)	3.0 [0.12, 72.77]
16 Perinatal death	3	337	Risk Ratio (M‐H, Fixed, 95% CI)	8.17 [0.45, 147.76]
23 Postpartum haemorrhage	2	300	Risk Ratio (M‐H, Fixed, 95% CI)	0.16 [0.03, 0.87]
28 Not in labour at 72 hours	4	437	Risk Ratio (M‐H, Fixed, 95% CI)	0.67 [0.60, 0.75]

1.2. Analysis.

Comparison 1 Breast stimulation versus no intervention (all women), Outcome 2 Uterine hyperstimulation with fetal heart rate changes.

1.3. Analysis.

Comparison 1 Breast stimulation versus no intervention (all women), Outcome 3 Caesarean section.

1.4. Analysis.

Comparison 1 Breast stimulation versus no intervention (all women), Outcome 4 Serious neonatal morbidity/perinatal death.

1.6. Analysis.

Comparison 1 Breast stimulation versus no intervention (all women), Outcome 6 Cervix unfavourable/unchanged after 12‐24 hours.

1.8. Analysis.

Comparison 1 Breast stimulation versus no intervention (all women), Outcome 8 Uterine hyperstimulation without fetal heart rate changes.

1.12. Analysis.

Comparison 1 Breast stimulation versus no intervention (all women), Outcome 12 Meconium stained liquor.

1.13. Analysis.

Comparison 1 Breast stimulation versus no intervention (all women), Outcome 13 Apgar score < 7 at 5 minutes.

1.16. Analysis.

Comparison 1 Breast stimulation versus no intervention (all women), Outcome 16 Perinatal death.

1.23. Analysis.

Comparison 1 Breast stimulation versus no intervention (all women), Outcome 23 Postpartum haemorrhage.

1.28. Analysis.

Comparison 1 Breast stimulation versus no intervention (all women), Outcome 28 Not in labour at 72 hours.

Comparison 2. Breast stimulation versus no intervention (all women, favourable cervix).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2 Uterine hyperstimulation with fetal heart rate changes	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
4 Serious neonatal morbidity/perinatal death	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
8 Uterine hyperstimulation without fetal heart rate changes	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
16 Perinatal death	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
28 Not in labour at 72 hours	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.64 [0.52, 0.79]

2.2. Analysis.

Comparison 2 Breast stimulation versus no intervention (all women, favourable cervix), Outcome 2 Uterine hyperstimulation with fetal heart rate changes.

2.4. Analysis.

Comparison 2 Breast stimulation versus no intervention (all women, favourable cervix), Outcome 4 Serious neonatal morbidity/perinatal death.

2.8. Analysis.

Comparison 2 Breast stimulation versus no intervention (all women, favourable cervix), Outcome 8 Uterine hyperstimulation without fetal heart rate changes.

2.16. Analysis.

Comparison 2 Breast stimulation versus no intervention (all women, favourable cervix), Outcome 16 Perinatal death.

2.28. Analysis.

Comparison 2 Breast stimulation versus no intervention (all women, favourable cervix), Outcome 28 Not in labour at 72 hours.

Comparison 3. Breast stimulation versus no intervention (all women, unfavourable cervix).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4 Serious neonatal morbidity/perinatal death	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	8.17 [0.45, 147.76]
6 Cervix unfavourable/unchanged after 12‐24 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	40.83 [2.64, 632.21]
12 Meconium stained liquor	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	1.96 [0.55, 7.03]
16 Perinatal death	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	8.17 [0.45, 147.76]
28 Not in labour at 72 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	0.74 [0.47, 1.16]

3.4. Analysis.

Comparison 3 Breast stimulation versus no intervention (all women, unfavourable cervix), Outcome 4 Serious neonatal morbidity/perinatal death.

3.6. Analysis.

Comparison 3 Breast stimulation versus no intervention (all women, unfavourable cervix), Outcome 6 Cervix unfavourable/unchanged after 12‐24 hours.

3.12. Analysis.

Comparison 3 Breast stimulation versus no intervention (all women, unfavourable cervix), Outcome 12 Meconium stained liquor.

3.16. Analysis.

Comparison 3 Breast stimulation versus no intervention (all women, unfavourable cervix), Outcome 16 Perinatal death.

3.28. Analysis.

Comparison 3 Breast stimulation versus no intervention (all women, unfavourable cervix), Outcome 28 Not in labour at 72 hours.

Comparison 4. Breast stimulation versus no intervention (all primiparae).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2 Uterine hyperstimulation with fetal heart rate changes	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
4 Serious neonatal morbidity/perinatal death	2	137	Risk Ratio (M‐H, Fixed, 95% CI)	8.17 [0.45, 147.76]
6 Cervix unfavourable/unchanged after 12‐24 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	40.83 [2.64, 632.21]
8 Uterine hyperstimulation without fetal heart rate changes	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
12 Meconium stained liquor	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	1.96 [0.55, 7.03]
16 Perinatal death	2	137	Risk Ratio (M‐H, Fixed, 95% CI)	8.17 [0.45, 147.76]
23 Postpartum haemorrhage	1	200	Risk Ratio (M‐H, Fixed, 95% CI)	0.25 [0.03, 2.20]
28 Not in labour at 72 hours	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.64 [0.52, 0.79]

4.2. Analysis.

Comparison 4 Breast stimulation versus no intervention (all primiparae), Outcome 2 Uterine hyperstimulation with fetal heart rate changes.

4.4. Analysis.

Comparison 4 Breast stimulation versus no intervention (all primiparae), Outcome 4 Serious neonatal morbidity/perinatal death.

4.6. Analysis.

Comparison 4 Breast stimulation versus no intervention (all primiparae), Outcome 6 Cervix unfavourable/unchanged after 12‐24 hours.

4.8. Analysis.

Comparison 4 Breast stimulation versus no intervention (all primiparae), Outcome 8 Uterine hyperstimulation without fetal heart rate changes.

4.12. Analysis.

Comparison 4 Breast stimulation versus no intervention (all primiparae), Outcome 12 Meconium stained liquor.

4.16. Analysis.

Comparison 4 Breast stimulation versus no intervention (all primiparae), Outcome 16 Perinatal death.

4.23. Analysis.

Comparison 4 Breast stimulation versus no intervention (all primiparae), Outcome 23 Postpartum haemorrhage.

4.28. Analysis.

Comparison 4 Breast stimulation versus no intervention (all primiparae), Outcome 28 Not in labour at 72 hours.

Comparison 5. Breast stimulation versus no intervention (all primiparae, favourable cervix).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2 Uterine hyperstimulation with fetal heart rate changes	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
4 Serious neonatal morbidity/perinatal death	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
8 Uterine hyperstimulation without fetal heart rate changes	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
16 Perinatal death	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
28 Not in labour at 72 hours	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.64 [0.52, 0.79]

5.2. Analysis.

Comparison 5 Breast stimulation versus no intervention (all primiparae, favourable cervix), Outcome 2 Uterine hyperstimulation with fetal heart rate changes.

5.4. Analysis.

Comparison 5 Breast stimulation versus no intervention (all primiparae, favourable cervix), Outcome 4 Serious neonatal morbidity/perinatal death.

5.8. Analysis.

Comparison 5 Breast stimulation versus no intervention (all primiparae, favourable cervix), Outcome 8 Uterine hyperstimulation without fetal heart rate changes.

5.16. Analysis.

Comparison 5 Breast stimulation versus no intervention (all primiparae, favourable cervix), Outcome 16 Perinatal death.

5.28. Analysis.

Comparison 5 Breast stimulation versus no intervention (all primiparae, favourable cervix), Outcome 28 Not in labour at 72 hours.

Comparison 6. Breast stimulation versus no intervention (all primiparae, unfavourable cervix).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4 Serious neonatal morbidity/perinatal death	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	8.17 [0.45, 147.76]
6 Cervix unfavourable/unchanged after 12‐24 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	40.83 [2.64, 632.21]
12 Meconium stained liquor	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	1.96 [0.55, 7.03]
16 Perinatal death	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
28 Not in labour at 72 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	0.74 [0.47, 1.16]

6.4. Analysis.

Comparison 6 Breast stimulation versus no intervention (all primiparae, unfavourable cervix), Outcome 4 Serious neonatal morbidity/perinatal death.

6.6. Analysis.

Comparison 6 Breast stimulation versus no intervention (all primiparae, unfavourable cervix), Outcome 6 Cervix unfavourable/unchanged after 12‐24 hours.

6.12. Analysis.

Comparison 6 Breast stimulation versus no intervention (all primiparae, unfavourable cervix), Outcome 12 Meconium stained liquor.

6.28. Analysis.

Comparison 6 Breast stimulation versus no intervention (all primiparae, unfavourable cervix), Outcome 28 Not in labour at 72 hours.

Comparison 7. Breast stimulation versus no intervention (all multiparae).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
23 Postpartum haemorrhage	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.09 [0.01, 1.60]
28 Not in labour at 72 hours	1	100	Risk Ratio (M‐H, Fixed, 95% CI)	0.61 [0.47, 0.81]

7.23. Analysis.

Comparison 7 Breast stimulation versus no intervention (all multiparae), Outcome 23 Postpartum haemorrhage.

7.28. Analysis.

Comparison 7 Breast stimulation versus no intervention (all multiparae), Outcome 28 Not in labour at 72 hours.

Comparison 8. Breast stimulation versus oxytocin (all women).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2 Uterine hyperstimulation with fetal heart rate changes	1	62	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
3 Caesarean section	1	62	Risk Ratio (M‐H, Fixed, 95% CI)	0.60 [0.31, 1.18]
4 Serious neonatal morbidity/perinatal death	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	3.53 [0.40, 30.88]
6 Cervix unfavourable/unchanged after 12‐24 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	0.13 [0.01, 2.25]
8 Uterine hyperstimulation without fetal heart rate changes	1	62	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
12 Meconium stained liquor	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	1.47 [0.47, 4.62]
16 Perinatal death	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	3.53 [0.40, 30.88]
28 Not in labour at 72 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	2.35 [1.00, 5.54]

8.2. Analysis.

Comparison 8 Breast stimulation versus oxytocin (all women), Outcome 2 Uterine hyperstimulation with fetal heart rate changes.

8.3. Analysis.

Comparison 8 Breast stimulation versus oxytocin (all women), Outcome 3 Caesarean section.

8.4. Analysis.

Comparison 8 Breast stimulation versus oxytocin (all women), Outcome 4 Serious neonatal morbidity/perinatal death.

8.6. Analysis.

Comparison 8 Breast stimulation versus oxytocin (all women), Outcome 6 Cervix unfavourable/unchanged after 12‐24 hours.

8.8. Analysis.

Comparison 8 Breast stimulation versus oxytocin (all women), Outcome 8 Uterine hyperstimulation without fetal heart rate changes.

8.12. Analysis.

Comparison 8 Breast stimulation versus oxytocin (all women), Outcome 12 Meconium stained liquor.

8.16. Analysis.

Comparison 8 Breast stimulation versus oxytocin (all women), Outcome 16 Perinatal death.

8.28. Analysis.

Comparison 8 Breast stimulation versus oxytocin (all women), Outcome 28 Not in labour at 72 hours.

Comparison 9. Breast stimulation versus oxytocin (all women, unfavourable cervix).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4 Serious neonatal morbidity/perinatal death	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	3.53 [0.40, 30.88]
6 Cervix unfavourable/unchanged after 12‐24 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	1.24 [0.98, 1.57]
12 Meconium stained liquor	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	1.47 [0.47, 4.62]
16 Perinatal death	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	3.53 [0.40, 30.88]
28 Not in labour at 72 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	2.35 [1.00, 5.54]

9.4. Analysis.

Comparison 9 Breast stimulation versus oxytocin (all women, unfavourable cervix), Outcome 4 Serious neonatal morbidity/perinatal death.

9.6. Analysis.

Comparison 9 Breast stimulation versus oxytocin (all women, unfavourable cervix), Outcome 6 Cervix unfavourable/unchanged after 12‐24 hours.

9.12. Analysis.

Comparison 9 Breast stimulation versus oxytocin (all women, unfavourable cervix), Outcome 12 Meconium stained liquor.

9.16. Analysis.

Comparison 9 Breast stimulation versus oxytocin (all women, unfavourable cervix), Outcome 16 Perinatal death.

9.28. Analysis.

Comparison 9 Breast stimulation versus oxytocin (all women, unfavourable cervix), Outcome 28 Not in labour at 72 hours.

Comparison 10. Breast stimulation versus oxytocin (all primiparae).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4 Serious neonatal morbidity/perinatal death	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	3.53 [0.40, 30.88]
6 Cervix unfavourable/unchanged after 12‐24 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	1.24 [0.98, 1.57]
12 Meconium stained liquor	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	1.47 [0.47, 4.62]
16 Perinatal death	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	3.53 [0.40, 30.88]
28 Not in labour at 72 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	2.35 [1.00, 5.54]

10.4. Analysis.

Comparison 10 Breast stimulation versus oxytocin (all primiparae), Outcome 4 Serious neonatal morbidity/perinatal death.

10.6. Analysis.

Comparison 10 Breast stimulation versus oxytocin (all primiparae), Outcome 6 Cervix unfavourable/unchanged after 12‐24 hours.

10.12. Analysis.

Comparison 10 Breast stimulation versus oxytocin (all primiparae), Outcome 12 Meconium stained liquor.

10.16. Analysis.

Comparison 10 Breast stimulation versus oxytocin (all primiparae), Outcome 16 Perinatal death.

10.28. Analysis.

Comparison 10 Breast stimulation versus oxytocin (all primiparae), Outcome 28 Not in labour at 72 hours.

Comparison 11. Breast stimulation versus oxytocin (all primiparae, unfavourable cervix).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
4 Serious neonatal morbidity/perinatal death	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	3.53 [0.40, 30.88]
6 Cervix unfavourable/unchanged after 12‐24 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	1.24 [0.98, 1.57]
12 Meconium stained liquor	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	1.47 [0.47, 4.62]
16 Perinatal death	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	3.53 [0.40, 30.88]
28 Not in labour at 72 hours	1	37	Risk Ratio (M‐H, Fixed, 95% CI)	2.35 [1.00, 5.54]

11.4. Analysis.

Comparison 11 Breast stimulation versus oxytocin (all primiparae, unfavourable cervix), Outcome 4 Serious neonatal morbidity/perinatal death.

11.6. Analysis.

Comparison 11 Breast stimulation versus oxytocin (all primiparae, unfavourable cervix), Outcome 6 Cervix unfavourable/unchanged after 12‐24 hours.

11.12. Analysis.

Comparison 11 Breast stimulation versus oxytocin (all primiparae, unfavourable cervix), Outcome 12 Meconium stained liquor.

11.16. Analysis.

Comparison 11 Breast stimulation versus oxytocin (all primiparae, unfavourable cervix), Outcome 16 Perinatal death.

11.28. Analysis.

Comparison 11 Breast stimulation versus oxytocin (all primiparae, unfavourable cervix), Outcome 28 Not in labour at 72 hours.

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Adewole 1993a.

Methods	Randomisation by random‐number table. Concealment not stated. Only outcome assessor blind. Not stated if analyst blinded.
Participants	200 term primigravidae.
Interventions	Experimental group: unilateral self breast stimulation 1 hour per day for 3 days. Control: no intervention.
Outcomes	Postpartum haemorrhage. Not delivered at 72 hours.
Notes	Cross‐over trial started after 3 days. Only data related to first trial reported in the review.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Unclear risk	B ‐ Unclear

Adewole 1993b.

Methods	As Adewole 1993a.
Participants	100 term multigravidae.
Interventions	Experimental group: unilateral self breast stimulation 1 hour per day for 3 days. Control: no intervention.
Outcomes	Postpartum haemorrhage. Not delivered at 72 hours.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Unclear risk	B ‐ Unclear

Chayen 1986.

Methods	Randomisation by case record number. Concealment not stated. Blinding not feasible. Not stated if analyst blinded.
Participants	62 term women, indications for IOL, post‐term (n = 18), pre‐eclampsia (n = 27), others (n = 17). 30 in experimental group and 32 in control group.
Interventions	Experimental group: IOL using an electric breast pump, (250 Hg of negative pressure) alternating every 15 minutes from left to right nipple. Control group: oxytocin infusion. Both groups: amniotomy once regular contractions occurred and cervix at least 2 cm dilated.
Outcomes	Uterine hyperstimulation with and without FHR changes. Caesarean section rate.
Notes	3 experimental group participants were excluded from analysis. Re‐analysis by ITT was possible.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	High risk	C ‐ Inadequate

Damania 1992.

Methods	Randomisation and concealment methods not stated. Blinding not feasible for participant, therapist or outcome assessor. Not stated if analyst was blinded.
Participants	57 primigravid, high‐risk women at > 37 weeks' gestation, all with reactive NST.
Interventions	Group 1: self‐breast stimulation, 3 x 1 hour per day, alternating breast every 10 mins. Group 2: IV oxytocin infusion. Group 3: no intervention.
Outcomes	Serious neonatal morbidity/ perinatal death. Meconium stained liquor. Perinatal death.
Notes	20 women were originally randomised to each group. The trial was stopped following 3 perinatal deaths in the breast stimulation arm. No outcome data were presented for the missing 3 women in this arm. Data are therefore analysed on an available case basis. All women remained in the groups they were randomised to.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Unclear risk	B ‐ Unclear

Elliott 1984a.

Methods	Randomisation by random‐number tables. Concealment not stated. Not feasible to blind participants or therapist. Not stated whether outcome assessor or analyst blinded.
Participants	200, low‐risk women at approximately 39 weeks' gestation. 100 in each group.
Interventions	Experimental group: daily self‐breast stimulation at home (minimum 3 hours per day, alternating breast every 15 minutes). Control group: no intervention with instructions to avoid breast stimulation and refrain from sexual intercourse.
Outcomes	Caesarean section rate. Serious neonatal morbidity. Meconium stained liquor. Apgar score < 7 at 5 minutes. Perinatal death.
Notes	Control group randomised a 2nd time at 42 weeks if BS < 8, and reactive CST. Data from this 2nd study were not reported in this review. Reporting based on original group allocation.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Unclear risk	B ‐ Unclear

Salmon 1986a.

Methods	Randomisation by random‐number tables. Concealment not stated. Double blinding not feasible. Outcome assessor blinded. Unclear if analyst blinded.
Participants	100 primipara, uncomplicated pregnancies, favourable cervix greater or equal to 8. 50 in each arm.
Interventions	Experimental group: self‐breast stimulation 3 hours per day, no sexual intercourse. Control group: no intervention, no sexual intercourse.
Outcomes	Uterine hyperstimulation with or without FHR changes. Serious neonatal morbidity or perinatal death.
Notes	This was a report of a cross‐over trial. Only the results of first trial are reported in this review.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Unclear risk	B ‐ Unclear

BS: Bishop score 
 CST: contraction stress test 
 FHR: fetal heart rate 
 IOL: induction of labour 
 ITT: intention to treat 
 IV: intravenous 
 mins: minutes 
 NST: non‐stress test

Characteristics of excluded studies [ordered by study ID]

Study	Reason for exclusion
Adewole 1993c	Results of a cross‐over trial. Data from original trial included in review (Adewole 1993a).
Damania 1988	Results of controlled trial, not randomised.
Di Lieto 1989	No prespecified outcomes reported.
Elliott 1983	No prespecified outcomes reported.
Elliott 1984b	Results of a second trial which re‐randomised the control group of Elliott 1984a.
Kadar 1990	No prespecified outcomes reported.
Salmon 1986b	Results of a cross‐over trial. Data from original trial included in review (Salmon 1986a).

Contributions of authors

J Kavanagh, AJ Kelly and J Thomas were involved in the data extraction and assessment of the trials. J Kavanagh entered data into Review Manager. J Kavanagh and AJ Kelly analysed data. AJ Kelly provided a clinical perspective for the interpretation of data. J Kavanagh drafted the review. J Kavanagh updated the review and AJ Kelly and J Thomas commented on the update.

Sources of support

Internal sources

• Clinical Effectiveness Support Unit, Royal College of Obstetricians and Gynaecologists, London, UK.

• EPPI‐Centre, Social Science Research Unit, Institute of Education, UK.

External sources

• No sources of support supplied

Declarations of interest

None known.

New search for studies and content updated (no change to conclusions)