Elective induction of labor and the risk of cesarean section in low-risk parous women: a cohort study

Abstract

Objective: To estimate the association between elective induction of labor and cesarean section in low-risk parous women, and to assess whether the association is influenced by induction method.

Design: Cohort study.

Setting: University hospital in Sweden.

Population: Parous women without pregnancy complications or previous cesarean section, and with a planned vaginal term (37-41 weeks), singleton birth, in vertex position were included.

Methods: Information was collected from a local database containing prospectively entered antenatal and delivery data. Odds ratios for cesarean section were calculated using generalized estimating equations logistic regression and adjusted for parity, maternal age, gestational length, birthweight, use of epidural anesthesia and year of birth.

Main outcome measures: Emergency cesarean section.

Results: Among 7973 pregnancies that fulfilled the inclusion criteria, 343 (4%) had an elective induction of labor. Intravenous oxytocin was administered in 5% of these inductions, amniotomy was performed in 62%, and a cervical ripening agent was used in 33%. Electively induced labor more than doubled the risk of cesarean section compared with spontaneous labor onset (OR 2.5, 95% CI 1.4-4.2) and this risk was more than tripled when cervical ripening was used (OR 3.6, 95% CI 1.7-7.6).

Conclusions: In low-risk parous women, electively induced labor has an increased risk of emergency cesarean section compared with spontaneous onset labor. This risk increase is more pronounced if cervical ripening agents are required. Women need to be counseled about these risks before elective induction of delivery is decided.