Hutton 2011.

Methods	2‐arm, unblinded, multicentre, parallel‐group randomised controlled trial. Stratification for parity and centre. Individual randomisation.
Participants	Setting: 68 centres in 21 countries. Hospital setting, with clinicians who were experienced in ECV and birth facilities that were deemed to meet Canadian standards. 1543 women randomised. Inclusion criteria: women with singleton fetus in a breech presentation who had a recent screening ultrasound, between 33+0/7 weeks' and 35+6/7 weeks' gestation. Exclusion criteria: women with contraindications to ECV (e.g. fetal heart rate abnormalities, placental abruption, major life‐threatening fetal anomalies, uterine anomalies, hyper‐extended fetal head, rupture of fetal membranes, severe oligohydramnios or hydramnios); contraindications to early ECV (e.g. increased risk of preterm labour or placental abruption); or contraindications to labour or vaginal birth (e.g. placenta praevia, previous classical caesarean section); or if they had been prior participants in the trial; were at increased risk of unstable lie (such as grand multiparity); or if they planned to give birth by caesarean section even if the fetus turned to a cephalic position, or if they planned a vaginal birth if the fetus remained breech.
Interventions	Early ECV: (n = 767) ECV carried out between 34+0/7 and 35+6/7 weeks of gestation, and within 7 days of randomisation. Fetal presentation was confirmed by ultrasound immediately before the ECV procedure. Fetal heart rate was monitored before, during and after the procedure. The use of tocolytics and analgesia was left to the discretion of the clinician, and they were directed to use the same approach for women in both arms of the trial. If the procedure was unsuccessful, or if a fetus later reverted to non‐cephalic, a repeat ECV procedure could be performed at a later date at the discretion of the care provider in consultation with the woman. Delayed ECV: (n = 774) ECV carried out at or after 37+0/7. Fetal presentation was confirmed by ultrasound immediately before the ECV procedure. Fetal heart rate was monitored before, during and after the procedure. The use of tocolytics and analgesia was left to the discretion of the clinician, and they were directed to use the same approach for women in both arms of the trial. If the procedure was unsuccessful, or if a fetus later reverted to non‐cephalic, a repeat ECV procedure could be performed at a later date at the discretion of the care provider in consultation with the woman. (Overall, tocolytics were used during all ECV attempts in 68% of cases.)
Outcomes	Primary: rate of caesarean section. Secondary: rate of preterm birth (< 37 weeks), non‐cephalic presentation at birth, admission to NICU for more than 24 hours, serious neonatal morbidity or death, maternal morbidity or death, pain and maternal satisfaction.
Notes	1 of the review authors was an investigator on this trial. Data extraction and assessment of risk of bias were carried out by 2 independent review authors. This study was funded by Canadian institutes of Health Research.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation with a computerised randomisation program, using computer‐generated random block sizes and 1:1 allocation.
Allocation concealment (selection bias)	Low risk	Central randomisation by telephone.
Blinding of participants and personnel (performance bias) All outcomes	High risk	“The nature of the intervention did not lend itself to blinding of either participants or clinicians.”
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Some efforts were made to avoid detection bias. Blinding of initial assessment and recording of outcomes is not described. An independent Data Safety and Monitoring Board “reviewed all stillbirths and neonatal deaths, blinded to allocation group, for the existence of any anomaly considered incompatible with life and to make a determination regarding exclusion of any women from the analysis of perinatal/neonatal outcomes”. An interim analysis of results was also carried out by the independent Data Safety and Monitoring Board, blinded to group assignment.
Incomplete outcome data (attrition bias) All outcomes	Low risk	2 women, 1 in each group, asked to be removed from the study. 8 women were lost to follow‐up (2 assigned to early ECV, 6 to delayed ECV). This left 1533 women (99.4%), so although the losses to follow‐up were unequal the numbers were small in the context of the whole study. A small amount of missing data (2 early ECV, 1 delayed ECV) accounted for in table 5. An intention‐to‐treat analysis was conducted. Perinatal and neonatal deaths were excluded from the analyses of measures of neonatal morbidity.
Selective reporting (reporting bias)	Low risk	All relevant outcomes appear to have been reported, including those showing no differences between groups. Multiple reports available for this study including trial registration.
Other bias	Low risk	Baseline characteristics were similar in the 2 groups. No other bias apparent.