Mobility of the perineal body and anorectal junction before and after childbirth

Introduction and hypothesis: The perineal body is an important structure which is often injured during labor. It is believed to play a role in pelvic organ support. Vaginal delivery is likely to increase the mobility of perineal body and anorectal junction. The aim of this study was to determine changes in the mobility of perineal body and anorectal junction before and after delivery using pelvic floor ultrasound. Methods: Two hundred nulliparous women were enrolled and underwent pelvic floor ultrasound at 36-38 weeks gestation and 3-6 months postpartum. Levator hiatal dimensions and mobility of the perineal body and anorectal junction were measured in volume ultrasound datasets using postprocessing software, blinded against all clinical data, before and after childbirth. Results: Ultrasound measures of mobility of perineal body and anorectal junction were shown to be reproducible (ICC 0.74 and 0.76). After delivery, mobility of both structures had increased significantly (both P<0.001), and postpartum perineal mobility was associated with delivery mode (P00.015). A significant correlation was found between these outcome measures and levator hiatal area on Valsalva, both before and after delivery. Perineal trauma, episiotomy, epidural block, augmentation of labor, and length of first and second stage of labor were not associated with postpartum mobility of perineal body and anorectal junction. Conclusions: Vaginal delivery increases the mobility of perineal body and anorectal junction. Perineal mobility may be partly determined by distensibility of the levator hiatus.