Episiotomy and increase in the risk of obstetric laceration in a subsequent vaginal delivery.

Objective: To examine whether episiotomy at first vaginal delivery increases the risk of spontaneous obstetric laceration in the subsequent delivery.

Methods: A review was conducted of women with consecutive vaginal deliveries at Magee-Womens Hospital between 1995 and 2005, using the Magee Obstetrical Maternal and Infant database. The primary exposure of interest was episiotomy at first vaginal delivery. Multivariable polytomous logistic regression modeling of potential risk factors was used to estimate odds ratios (ORs) for obstetric laceration in the second vaginal delivery.

Results: A total of 6,052 patients were included, of whom 47.8% had episiotomy at first delivery. Spontaneous second-degree lacerations at the time of second delivery occurred in 51.3% of women with history of episiotomy at first delivery compared with 26.7% without history of episiotomy (P<.001). Severe lacerations (third or fourth degree) occurred in 4.8% of women with history of episiotomy at first delivery compared with 1.7% without history of episiotomy (P<.001). Prior episiotomy remained a significant risk factor for second-degree (OR 4.47, 95% confidence interval 3.78-5.30) and severe obstetric lacerations (OR 5.25, 95% confidence interval 2.96-9.32) in the second vaginal delivery after controlling for confounders. Based on these findings, for every four episiotomies not performed one second-degree laceration would be prevented. To prevent one severe laceration, performing 32 fewer episiotomies is required.

Conclusion: Episiotomy at first vaginal delivery increases the risk of spontaneous obstetric laceration in the subsequent delivery. This finding should encourage obstetric providers to further restrict the use of episiotomy.

Level Of Evidence: II.