Mode of delivery in a subsequent pregnancy following previous instrumental delivery

To assess mode of subsequent delivery in women with previous instrumental vaginal delivery.

In this retrospective longitudinal study we followed women who underwent instrumental delivery. The study group included all consecutive parturient women who underwent an instrumental vaginal delivery during a 24-month period (1996-1999). We then identified women who had a subsequent delivery in our center until the end of the year 2010. The control group included women who had a spontaneous vaginal delivery from the same time.

During the index period we had 349 consecutive successful instrumental vaginal deliveries. Of those, 125 women had a subsequent delivery in our center (35.8%). In subsequent pregnancies, the spontaneous vaginal delivery rate was 76.8% and 90.4%; the instrumental delivery rate was 8.8% and 1.6%; and the cesarean rate was 14.4% and 8.0%, in the instrumental delivery, and spontaneous vaginal delivery groups, respectively (P<0.05). The odds ratio for a woman to undergo either an instrumental delivery or a cesarean after having an instrumental delivery in a previous pregnancy was 2.8 (95% confidence interval 1.4-5.9, P<0.05).

Women with a previous instrumental delivery are at an increased risk of requiring either an instrumental delivery or a cesarean section in a subsequent pregnancy compared with women with a previous spontaneous vaginal delivery.