Pregnancy outcome and mode of delivery after a previous operative vaginal delivery

OBJECTIVE: To assess pregnancy outcome and risk factors for repeat operative vaginal delivery in women with previous operative vaginal delivery. METHODS: This was a case-control study of all nulliparous women who underwent operative vaginal delivery in a tertiary care medical center from 1993-2006 (n=4,153). The control group included nulliparous women who underwent spontaneous vaginal delivery during the same period in a 2:1 ratio (n=8,306). The women in each group who had a subsequent delivery at our center were identified (n=1,396 and n=2,591, respectively), and the outcome of the subsequent delivery was recorded. RESULTS: Compared with the women in the spontaneous vaginal delivery group, women who underwent operative vaginal delivery in the index pregnancy had a higher rate of operative vaginal delivery (4.7% compared with 1.2%, P<.006) and cesarean delivery (8.5% compared with 4.6%, P<.001) in the subsequent pregnancy. The rate of neonatal birth injury (1.5% compared with 0.6%, P=.005) and third-degree or fourth-degree lacerations (0.7% compared with 0.2%, P=.01) was significantly higher in the group of women with a previous operative vaginal delivery. Risk factors for repeat operative vaginal delivery were as follows: failed vacuum extraction and prolonged second stage as the indication for operative vaginal delivery in the index pregnancy; prolonged interval (more than 3 years) between pregnancies; higher fetal weight, persistent occipitoposterior position, and use of epidural analgesia in the subsequent pregnancy. The presence of epidural analgesia in the index operative vaginal delivery was not associated with a decreased risk of repeat operative vaginal delivery. CONCLUSION: Nulliparous women undergoing operative vaginal delivery are at increased risk of operative vaginal delivery and cesarean delivery in their subsequent pregnancy. Risk stratification based on the identified risk factors may assist clinicians in predicting the likelihood of repeat operative vaginal delivery and in counseling patients accordingly.