Risk factors for severe obstetric perineal lacerations.

INTRODUCTION AND HYPOTHESIS: The aim of this study was to assess the occurrence of severe perineal lacerations in vaginal delivery and its relationship with predisposing clinical and obstetric factors.

METHODS: A retrospective cohort analysis using an electronic clinical database at a University Referral Center for high-risk pregnancies was performed. A total of 941 vaginal deliveries were analyzed, over 10 consecutive months in 2013 and 2014. The relationship between obstetric and clinical characteristics and lacerations, especially severe forms, was analyzed. The frequency and severity of birth canal lacerations were compiled and classified as mild (unintentional laceration grades I and II, and mediolateral episiotomy) and severe (grades III and IV). The crude and adjusted odds ratios and 95% confidence intervals were estimated in univariate and multivariate logistic regression models.

RESULTS: The overall incidence of perineal lacerations in vaginal delivery was 78.2% (n = 731). Lacerations were considered mild in 708 women (75.7%) and severe in 23 women (2.5%). Maternal age, parity, use of forceps, mediolateral episiotomy, and birth weight influenced the occurrence of some degree of tear. The chance of severe lacerations increased 1.77-fold per week with the gestational age (1.03-3.03, P = 0.025), while primiparity increased the chance of laceration 5.32-fold. Episiotomy did not show a protective effect against severe laceration occurrence (P = 0.999).

CONCLUSIONS: Severe perineal lacerations were associated with operative delivery, primiparity, gestational age, and epidural anesthesia. Episiotomy was not protective.