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