Association between median episiotomy and severe perineal lacerations in primiparous women.

OBJECTIVE To evaluate the association between median episiotomy and severe (third- and fourth-degree) perineal lacerations in primiparous women. DESIGN Retrospective cohort study. SETTING University-affiliated hospital providing secondary obstetric care in Quebec City. PATIENTS A total of 6522 primiparous women who gave birth vaginally to a single live baby in cephalic position between 1985 and 1993. OUTCOME MEASURE Incidence of third- and fourth-degree perineal lacerations. RESULTS Median episiotomy was performed in 4390 women (67.3%). A total of 1002 women (15.4%) had a third- or fourth-degree laceration. The frequency of severe perineal lacerations was 20.6% with episiotomy and 4.5% without episiotomy (relative risk [RR] 4.58, 95% confidence interval [CI] 3.74-5.62). This association persisted after adjustment by stratified analysis for type of delivery and birth weight (RR 3.03, 95% CI 2.52-3.63) and by logistic regression for type of delivery, birth weight, epidural analgesia, shoulder dystocia, baby's head circumference, experience of the physician and year of delivery (odds ratio 3.58, 95% CI 2.84-4.50). CONCLUSION Median episiotomy is strongly associated with third- and fourth-degree perineal lacerations in primiparous women. Reducing the use of this procedure could decrease the occurrence of severe perineal tears.