1. 1. First-degree perineal laceration: injury to only the vaginal epithelium or perineal skin. 2. Second-degree laceration: injury to perineum that spares the anal sphincter complex but involves the perineal muscles, which are the bulbospongiosus and superficial transverse perineal muscles. 3a. Third-degree laceration: <50 percent of the external anal sphincter (EAS) is torn. 3b. Third-degree laceration: >50 percent of the EAS is torn, but the internal anal sphincter (IAS) remains intact. 3c. Third-degree laceration: EAS and IAS are torn. 4. Fourth-degree laceration: the perineal body, entire anal sphincter complex, and anorectal mucosa are lacerated. (Reproduced with permission from Kenton K, Mueller M: Episiotomy and obstetric anal sphincter lacerations. In Yeomans ER, Hoffman BL, Gilstrap LC III, et al (eds): Cunningham and Gilstrap’s Operative Obstetrics, 3rd ed. New York, McGraw-Hill Education, 2017.)
Source: Vaginal Delivery, Williams Obstetrics, 25e
Citation: Cunningham F, Leveno KJ, Bloom SL, Spong CY, Dashe JS, Hoffman BL, Casey BM, Sheffield JS. Williams Obstetrics, 25e; 2016 Available at: Accessed: October 18, 2017
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