Perineal lacerations during spontaneous vaginal delivery

The aim of the study was to assess the frequency of perineal lacerations during normal spontaneous vaginal delivery and to evaluate potential risk factors.

The study is based on an analysis of data from the obstetric database of the University Hospital of Vienna and the Semmelweis Women's Hospital Vienna, from February 1999 through to July 1999. Women with vaginal deliveries, uncomplicated pregnancies, uncomplicated first and second stage of labor, gestational age > 37 weeks and pregnancies with cephalic presentation were included.

Of 1009 women, 36.2% had perineal lacerations (18.1% had first-degree, 15.2% second-degree, and 2.9% third-degree perineal tears). Univariate logistic regression models showed that only low parity (p = 0.004), the absence of episiotomy (p = 0.0001), and a large head diameter of the infant (p = 0.005) increased the risk for perineal laceration. After adjustment in multivariate analysis, low parity (p = 0.0001), the absence of episiotomy (p = 0.0001) and a large head diameter (p = 0.0004) remained independent risk factors for perineal laceration. Additionally, advanced age of the mother was associated with an increased risk of perineal laceration (p = 0.03). When analyzing the probability for third-degree perineal tears, a strong association with primiparity (p = 0.01), the use of episiotomy (p = 0.0001), a prolonged second stage of labor (p = 0.0001), a large head diameter of the infant (p = 0.01) and the use of oxytocin (p = 0.008) was found.

Primiparous women who are being delivered of a large child are at a greater risk for severe perineal lacerations. In the study population episiotomy did not appear to protect against severe perineal lacerations.