Objective: To identify risk factors for mediolateral episiotomy, and evaluate the risk of obstetrical anal sphincter injury (OASI) among women with an episiotomy.
Methods: A retrospective cohort study of all singletons vaginal deliveries at term between 2007 and 2014. Spontaneous and operative vaginal deliveries were compared separately, as well as nulliparous and multiparous women.
Results: Overall, 41,347 women were included in the spontaneous vaginal delivery group: 12,585 (30.4%) nulliparous and 28,762 (69.6%) multiparous women. Risk factors for episiotomy (nulliparous) were maternal age (aOR 0.98), gestational age (GA, aOR 1.07), regional analgesia (RA, aOR 1.18), labor induction (aOR 1.17), meconium (aOR 1.37) and birth weight (BW, aOR 1.04). Episiotomy was associated with PPH (aOR 1.49). Among multiparous, risk factors were maternal age (aOR 1.04), previous vaginal delivery (aOR 0.38), GA (aOR 1.06), RA (aOR 1.22), meconium (aOR 1.22) and BW (aOR 1.05). Episiotomy was associated with 3rd degree perineal tear (aOR 2.26, 95% CI 1.03-4.97). Only birth weight (nulliparous) and previous vaginal deliveries (multiparous) were contributors for episiotomy in the OVD group.
Conclusion: Several risk factors for mediolateral episiotomy exist. Episiotomy does not protect nulliparous women, and may be associated with an increased risk for multiparous, for OASI. Therefore, the practice of routine episiotomy should be abandoned, and the practice of selective episiotomy reconsidered.
Keywords: Mediolateral episiotomy; obstetrical anal sphincter injury; operative vaginal delivery; parity; spontaneous vaginal delivery.