Vaginal delivery is associated with occult disruption of the anal sphincter mechanism.

Childbirth is thought to be an important cause of pelvic floor dysfunction. Heretofore, this has been thought due to pudendal denervation. Endovaginal sonography allows thorough assessment of the anorectum and in this study was used to assess nulliparous women and women before and after delivery. Two groups were studied. Thirty-two nulliparous subjects without complaints of incontinence were studied once. Thirty-four pregnant women were studied before and after delivery. Endovaginal sonography was used to assess integrity of internal and external anal sphincters, thickness of the levator bundle, internal and external sphincters, anal length, and the angle between the levator bundles. Delivery was associated with disruption of the internal and external sphincters. No nulliparous women (nonpregnant or pregnant) had sphincter disruption demonstrated. Episiotomy in the index delivery was associated with increased thickness in the external sphincter and a smaller angle between the levator bundles. Vaginal delivery is associated with occult disruption of the anal sphincters.