Chua 1997.

Methods	RCT. Random number table, no details on the method of concealment of the allocation.
Participants	Singleton vertex presentation, unfavourable cervix (BS < 6). 185 women recruited (90 in Dilapan group, 95 in PGE2 group).
Interventions	Dilapan group: 4 dilators. PGE2 Gel (Prepidil): 0.5 mg. In both groups, ripening was followed by rupture of membranes and oxytocin after 12 hours.
Outcomes	Need for oxytocin, CS, instrumental delivery, uterine rupture, uterine hyperstimulation, admission to NICU, perinatal death.
Notes	Setting: National University hospital, Singapore Study period: not reported Funding: not reported Declarations of interest: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random number table
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not feasible due to nature of intervention
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	ITT not mentioned but seems reasonable as numbers in tables are equal to randomised numbers, no reporting of missing cases or outcomes
Selective reporting (reporting bias)	Low risk	All pre‐specified outcomes reported
Other bias	Low risk	No other bias detected