• Bela Kudish, Sean Blackwell, S Gene Mcneeley, Emmanuel Bujold, Michael Kruger, Susan L Hendrix, and Robert Sokol.
• Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI, USA.
• Am. J. Obstet. Gynecol. 2006 Sep 1; 195 (3): 749-54.

ObjectiveThe purpose of this study was to determine the impact of operative vaginal delivery (forceps or vacuum) and midline episiotomy on the risk of severe perineal trauma.Study DesignIn this retrospective cohort study, we assessed the impact of maternal and obstetric factors on the risk of development of severe perineal trauma (third- and fourth-degree perineal lacerations) for all singleton, vertex vaginal live births (n = 33,842) between 1996 and 2003.ResultsAmong nulliparous women, 12.1% had operative vaginal delivery, 22.4% had midline episiotomy, and 8.1% experienced severe perineal trauma. Among multiparous women, 3.4% had operative vaginal delivery, 4.2% had midline episiotomy, and 1.2% experienced severe perineal trauma. Controlling for maternal age, ethnicity, birth weight and head circumference, evaluation of the interaction of episiotomy and delivery method revealed that forceps (nulliparous women: odds ratio [OR] 8.6, 95% CI 6.5-10.7; multiparous women: OR 26.3, 95% CI 18.1-34.5) and episiotomy (nulliparous women: OR 4.5, 95% CI 3.7-5.4; multiparous women: OR 14.6, 95% CI 10.4-20.5) were consistently associated with the increased risk of anal sphincter trauma. In fact, the magnitude of effect of the statistically significant synergistic interaction was evidenced by more than 3-fold excess of risk of using operative vaginal delivery alone.ConclusionThe use of operative vaginal delivery, particularly in combination with midline episiotomy, was associated with a significant increase in the risk of anal sphincter trauma in both primigravid and multigravid women. Given the reported substantial long-term adverse consequences for anal function, this combination of operative modalities should be avoided if possible.

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