Induction of labor and the risk for emergency cesarean section in nulliparous and multiparous women.

OBJECTIVE: To assess the risk for emergency cesarean section among women in whom labor was induced in gestational week ≥41 and to evaluate if parity and mode of induction affected this association.

DESIGN: Hospital-based retrospective cohort study.

POPULATION: Singleton pregnancies delivered after ≥41 gestational weeks at Danderyd Hospital, Stockholm, Sweden, during 2002-2006.

MATERIAL AND METHODS: Of 23 030 singleton pregnancies meeting the entry criteria, 881 were induced with a Bishop score of <7. Obstetric outcome was assessed through linkage with the Swedish Medical Birth Registry and a local obstetrical database containing information from patients' medical files. Results were adjusted for body mass index, age and the use of epidural analgesia.

MAIN OUTCOME MEASURE: Risk for emergency cesarean section.

RESULTS: Among women who were induced, the proportions delivered by emergency cesarean section were 42% for nulliparous and 14% for multiparous. Compared to spontaneous onset, this corresponded to a more than threefold increase in risk for nulliparous women (OR 3.34, 95%CI 2.77-4.04) and an almost twofold increase in risk for multiparous women (OR 1.94, 95%CI 1.24-3.02). There was no significant difference in risk for emergency cesarean section between the two methods of induction (PGE(2) and transcervical catheter).

CONCLUSIONS: Compared to spontaneous onset of delivery, induction of labor is associated with an increased risk for emergency cesarean section both among nulliparous and multiparous women. When labor is induced, the high risk for emergency cesarean must be kept in mind.