The Prediction and Prevention of Caesarean Section in Labour

Abstract

Increasing caesarean section rates are a global phenomenon. It is widely believed many procedures are unnecessary and there are many opinions about what (if anything) to do about it. Attempts to limit the trend have had little noticeable success. This thesis is about reducing caesarean section in labour, and focuses on the concept that it can be predicted, and then prevented by induction of labour. Patterns of caesarean section over 27 years were described in two Sydney hospitals. The increase in primary caesarean sections was mostly due to increases in emergency procedures for slow labour, and elective procedures for malpresentation. Most of the overall increase was due to repeat procedures. Induction of labour before 40 weeks’ pregnancy reduced caesarean section rates for slow labour. Vaginal birth rates varied widely by indication for induction. Neonatal head circumference, cervical length, estimated fetal weight, and a combination of biparietal diameter and abdominal circumference were associated with caesarean section for slow labour. Demographic, clinical and ultrasound factors were included in a predictive model used in a protocol for a randomised trial of induction of labour at 39 weeks’ pregnancy. We also developed a method of creating centile birthweight standards which reflect fetal growth described by ultrasounds. Such charts could be used as part of a tool to screen for risk of perinatal mortality and enrolment into a randomised trial for improving perinatal outcomes. The work in this thesis adds to human knowledge by describing in detail how caesarean section rates and indications evolved over time. It adds to the understanding of associations between induction of labour, ultrasound, and demographic factors with caesarean section for slow progress in labour, allowing inferences to be made about how induction of labour prevents caesarean sections. It adds a new method for creating birth weight standards and a protocol for a randomised trial.