Objective: To determine whether antepartum X-ray pelvimetry (XRP) reliably identified women suitable for a trial labour or repeat elective caesarean section after one previous section.
Design: A prospective controlled trial in which women were randomly allocated to either an antepartum XRP group who had XRP at 36 weeks gestation to determine mode of delivery, or a control group who had a trial labour without antepartum XRP. Following delivery, all controls had postpartum XRP.
Setting: Department of Obstetrics and Gynaecology, King Edward VIII Hospital, Durban, South Africa.
Subjects: Three hundred-six women with a history of one previous caesarean section.
Main outcome measures: Mode of delivery, birthweight and maternal and perinatal mortality and morbidity in the two groups.
Results: In the antepartum XRP group, 23 of 144 (16%) of women delivered vaginally compared with 60 of 144 (42%) controls (P < 0.0001). Of the 84 women with adequate antepartum XRP only 23 (27.7%) delivered vaginally. In the control group, 33 of 60 (55%) women who had vaginal deliveries had inadequate postpartum XRP and would have had a caesarean section if this information was known in the antepartum period; 62 of 84 (74%) caesarean sections in the control group had adequate postpartum XRP. Birthweight of the infants was similar in the two groups. There were no maternal or perinatal deaths. Maternal morbidity was similar in the two groups. Neonatal morbidity was minimal.
Conclusion: Antepartum XRP is not necessary prior to a trial labour in women with one previous caesarean section. It increases the caesarean section rate and is a poor predictor of the outcome of labour.