Predicting the outcome of induction of labour.

Objective: To test whether prediction of delivery outcome is feasible in post-term nulliparous pregnant women, using a published model and a locally produced model combining clinical and ultrasound assessment.

Methods: This is a prospective pilot study of 53 nulliparous women seen in a postdates clinic between 40 weeks four days and 41 weeks three days of gestation. They underwent a routine assessment including transabdominal ultrasound to determine amniotic fluid index, a Bishop score, and translabial ultrasound to determine the station of the fetal head at rest and bladder neck descent at rest and on valsalva. Additional information such as body weight at booking and current weight, height and a family history of caesarean section was obtained. Delivery outcome and labour details were obtained from the local obstetric database. Two models for prediction of delivery outcome were tested.

Results: Forty-nine complete datasets were analysed. Fourteen women had a normal vaginal delivery, 17 instrumental deliveries and 18 caesarean sections. A published model predicted the induction outcome in 62%. A local model using maternal age, body mass index, family history of caesarean section, station of the fetal head and bladder neck descent predicted vaginal delivery in 70% in our study.

Conclusion: Prediction of delivery outcome is of limited feasibility in post-term nulliparous pregnant women. Our locally produced model was successful in predicting vaginal delivery in 70% of women. Prediction of delivery outcome may not be sufficiently powerful to allow modification of current obstetric practice.