Eileen K Hutton, G Justus Hofmeyr, Therese Dowswell

External cephalic version (ECV) of the breech fetus at term (after 37 weeks) has been shown to be effective in reducing the number of breech presentations and caesarean sections, but the rates of success are relatively low. This review examines studies initiating ECV prior to term (before 37 weeks' gestation). To assess the effectiveness of a policy of beginning ECV before term (before 37 weeks' gestation) for breech presentation on fetal presentation at birth, method of delivery, and the rate of preterm birth, perinatal morbidity, stillbirth or neonatal mortality. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 March 2015) and reference lists of retrieved studies. Randomised controlled trials (RCTs) of ECV attempted before term (37 weeks' gestation) or commenced before term, compared with a control group of women (in breech presentation) in which either no ECV attempted or ECV was attempted at term. Cluster-randomised trials were eligible for inclusion but none were identified. Quasi-RCTs or studies using a cross-over design were not eligible for inclusion. Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked for accuracy. Studies were assessed for risk of bias and for important outcomes the overall quality of the evidence was assessed using the GRADE approach. Five studies are included (2187 women). It was not possible for the intervention to be blinded, and it is not clear what impact lack of blinding would have on the outcomes reported. For other 'Risk of bias' domains studies were either at low or unclear risk of bias.One study reported on ECV that was undertaken and completed before 37 weeks' gestation compared with no ECV. No difference was found in the rate of non-cephalic presentation at birth (risk ratio (RR) 1.04, 95% confidence interval (CI) 0.64 to 1.69; participants = 102). One study reported on a policy of ECV that was initiated before term (33 weeks) and up until 40 weeks' gestation and which could be repeated up until delivery compared with no ECV. This study showed a decrease in the rate of non-cephalic presentation at birth (RR 0.59, 95% CI 0.45 to 0.77; participants = 179).Three studies reported on ECV started at between 34 to 35 weeks' gestation compared with beginning at 37 to 38 weeks' gestation. Pooled results suggested that early ECV reduced the risk of non-cephalic presentation at birth (RR 0.81, 95% CI 0.74 to 0.90; participants = 1906; studies = three; I² = 0%, evidence graded high quality), failure to achieve vaginal cephalic birth (RR 0.90, 95% CI 0.83 to 0.97; participants = 1888; studies = three; I² = 0%, evidence graded high quality), and vaginal breech delivery (RR 0.44, 95% CI 0.25 to 0.78; participants = 1888; studies = three; I² = 0%, evidence graded high quality). The difference between groups for risk of caesarean was not statistically significant (RR 0.92, 95% CI 0.85 to 1.00; participants = 1888; studies = three; I² = 0%, evidence graded high quality). There was evidence that risk of preterm labour was increased with early ECV compared with ECV after 37 weeks (6.6% in the ECV group and 4.3% for controls) (RR 1.51, 95% CI 1.03 to 2.21; participants = 1888; studies = three; I² = 0%, evidence graded high quality). There was no clear difference between groups for low infant Apgar score at five minutes or perinatal death (stillbirth plus neonatal mortality up to seven days) (evidence graded as low quality for both outcomes). Compared with no ECV attempt, ECV commenced before term reduces non-cephalic presentation at birth. Compared with ECV at term, beginning ECV at between 34 to 35 weeks may have some benefit in terms of decreasing the rate of non-cephalic presentation, and risk of vaginal breech birth. However, early ECV may increase risk of late preterm birth, and it is important that any future research reports infant morbidity outcomes. Results of the review suggest that there is a need for careful discussion with women about the timing of the ECV procedure so that they can make informed decisions.