Objective To determine if the decreased risk of adverse perinatal outcome, with a policy of planned caesarean, in the Term Breech Trial, was due to a reduction of problems of labour, problems of delivery or unrelated problems.
Design Secondary analysis of data from the Term Breech Trial, a randomised controlled trial of planned caesarean versus planned vaginal birth for the singleton fetus in frank or complete breech presentation at term.
Setting Women were recruited from 121 centres in 26 countries.
Population Women who were enrolled in the Term Breech Trial.
Methods Adverse perinatal outcome was classified as due to labour, due to delivery, due to neither labour nor delivery or unexplained by an experienced obstetrician who was masked to allocation group. The risk of an adverse outcome in each category was compared according to intention to treat and also by actual method of delivery.
Main outcome measures Adverse perinatal outcome (excluding lethal congenital anomalies) that was due to labour, due to delivery, due to neither labour nor delivery or unexplained.
Results Planned caesarean was associated with a lower risk of adverse outcome due to both labour (RR 0.14, 95% CI 0.04–0.45, P < 0.001) and delivery (RR 0.37, 95% CI 0.16–0.87, P= 0.03), compared with planned vaginal birth. Prelabour caesarean and caesarean during early labour were associated with the lowest risk and vaginal birth was associated with the highest risk of adverse outcome due to both labour (0%, 0.4% and 2.2%, respectively) and delivery (0.2%, 0% and 3.1%, respectively).
Conclusions Planned caesarean decreases the risk of adverse perinatal outcome due to both problems of labour and problems of delivery for the singleton fetus in breech presentation at term, compared with planned vaginal birth.