Haugland 2012.

Methods	RCT
Participants	Inclusion: singleton pregnancy, > 37 weeks, indication to induce birth, BS < 2 cm, term date set by US before week 21 Exclusion: IUFD, fetal malformations, low lying placenta, rupture of membranes, no understanding of Norwegian language
Interventions	Foley catheter (n = 90), 16‐19 hours Cook double balloon (n = 88), 16‐19 hours
Outcomes	Cervix dilatation ≥ 3 cm after removal or active labour
Notes	Abstract only Setting: Haukeland university hospital, Bergen, Norway Study period: March 2010 ‐ January 2011 Funding: not reported Declarations of interest: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomisation not described
Allocation concealment (selection bias)	Unclear risk	No information
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Double‐blind, says in the protocol that participants and outcome assessor will be blind to allocated treatment, but not clinicians
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Double‐blind, in the study protocol says participant and outcome assessor will be blind to allocated treatment
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	ITT not described mentioned, to little information to judge
Selective reporting (reporting bias)	Unclear risk	Insufficient information
Other bias	Unclear risk	Abstract only, too little information to judge risk of bias