Paper 42: Women Undergoing VBAC Are at Equal Risk for Severe Perineal Laceration Compared to Nulliparous Women

Abstract

OBJECTIVE: To assess the effect of parity and route of delivery on the risk of severe perineal lacerations. METHODS: The study was a cross-sectional analysis of data from a perinatal database that included all vaginal deliveries occurring at Magee-Womens Hospital (MWH) from 1995–2002. The 3 groups are: 1) G1P1 vaginal delivery, 2) G2P2 two vaginal deliveries, and 3) G2P2 with Cesarean delivery followed by vaginal birth (VBAC). Severe perineal laceration was the primary outcome and was defined as a 3rd or 4th degree anal sphincter tear. The adjusted risk for severe perineal laceration at delivery was estimated using a logistic regression model. RESULTS: 21,970 live, singleton, term pregnancies delivered at MWH from1995-2002. The groups included 14,117 primiparous women (64%), 6,324 women with 2 vaginal deliveries (29%), and 1,529 women with 1 Cesarean delivery followed by VBAC (7%). Severe perineal laceration occurred in 17% of women undergoing VBAC, 15% in primigravid women, compared to 3% in women undergoing a second vaginal delivery. Multivariable logistic regression models of severe perineal laceration yielded the following significant factors presented as odds ratios with 95% confidence intervals (Table 1).TABLE 1: Multivariable Logistic Regression Model of Severe Laceraton (3rd and 4th Degree)CONCLUSIONS: Women undergoing VBAC are at an equal risk of severe perineal laceration compared to nulliparous women. In this epidemiologic study, vaginal delivery, and not pregnancy by itself, appears to be the most important factor in decreasing the risk of severe perineal laceration in subsequent pregnancies.