*Article* **Midline and Mediolateral Episiotomy: Risk Assessment Based on Clinical Anatomy**

**Danielle K. Garner <sup>1</sup> , Akash B. Patel <sup>1</sup> , Jun Hung <sup>1</sup> , Monica Castro <sup>2</sup> , Tamar G. Segev <sup>1</sup> , Jeffrey H. Plochocki 3,\* and Margaret I. Hall 2,\***


**Abstract:** Episiotomy is the surgical incision of the vaginal orifice and perineum to ease the passage of an infant's head while crowning during vaginal delivery. Although episiotomy remains one of the most frequently performed surgeries around the world, short- and long-term complications from the procedure are not uncommon. We performed midline and mediolateral episiotomies with the aim of correlating commonly diagnosed postepisiotomy complications with risk of injury to perineal neuromuscular and erectile structures. We performed 61 incisions on 47 female cadavers and dissected around the incision site. Dissections revealed that midline incisions did not bisect any major neuromuscular structures, although they did increase the risk of direct and indirect injury to the subcutaneous portion of the external anal sphincter. Mediolateral incisions posed greater risk of iatrogenic injury to ipsilateral nerve, muscle, erectile, and gland tissues. Clinician discretion is advised when weighing the potential risks to maternal perineal anatomy during vaginal delivery when episiotomy is indicated. If episiotomy is warranted, an understanding of perineal anatomy may benefit diagnosis of postsurgical complications.

**Keywords:** bulbs of the vestibule; midline episiotomy; mediolateral episiotomy; perineal nerve
