Abstract: 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.

Plain-language summary: This review included five randomised controlled studies with an overall total of 2187 women, the studies were at low or unclear risk of bias although it was not possible to "blind" women and staff to this intervention. Results showed that if ECV is done near the middle of the third trimester (32 to 34 weeks), it increases the chances that the baby will be lying head down at full term. Three trials including 1888 women found that beginning ECV at between 34 and 36 weeks compared with beginning ECV after 37 weeks (at term) had a 19% decrease in the rate of non-cephalic presentation at birth, a 10% reduction in the risk of failing to achieve a cephalic vaginal birth, and a considerably reduced chance of a breech vaginal delivery, however, early ECV may significantly increase the chances of late preterm birth. The quality of the evidence for these outcomes was graded as high. The evidence on the possible advantages and disadvantages of early (before 37 weeks) external cephalic version (ECV) will require careful discussion with women about the timing of the ECV procedure so that they can make informed decisions.