Midline Episiotomy May Pose Less Risk of Nerve Damage Than Mediolateral Episiotomy: A Cadaveric Anatomical Study

Abstract

Episiotomy, the surgical incision of the perineum to assist during vaginal delivery, can be classified into two main approaches, midline and mediolateral. While use of surgical episiotomies is in a decline, clinicians throughout the world continue to commonly utilize episiotomy. However, current literature provides insufficient anatomic evidence as to which of the two approaches is preferable. Many clinicians utilize a mediolateral approach, arguing that this incision ensures the safety of the external anal sphincter and therefore will not endanger maternal fecal continence postpartum. Other clinicians prefer a midline approach, arguing that incising the perineal body will endanger fewer anatomical structures. In this study, we utilize human cadaveric dissection to identify and understand which anatomical structures are damaged through the use of the two episiotomy approaches to justify a preferential episiotomy procedure. We performed a midline and one of four mediolateral episiotomy incisions using blunt scissors on 15 female cadavers used for medical education at Midwestern University. The posterior minor labia in the midline provided a zero‐degree axis from which angles of incision were calculated to either 60, 45, 30, or 20 degrees from midline using digital calipers and a protractor. After incision, dissection revealed structure damage. All dissections revealed that mediolateral episiotomy damaged the ipsilateral bulb of the vestibule and the overlying bulbospongiosus muscle. The superficial perineal nerve was damaged in 20% of the cadavers, and the anterior labial nerve was damaged in 13% of the cadavers. However, we suspect that during birth when the region is engorged with blood and the vaginal orifice pulled inferiorly and anteriorly, mediolateral episiotomy could result in nerve damage more often than in cadaveric dissection. Based on these results, we suggest that a midline approach might be preferable. Possible denervation to perineal structure may outweigh the potential risks to the external anal sphincter, which would likely heal within weeks postpartum with its nerve supply intact.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.