ANAL-SPHINCTER DISRUPTION DURING VAGINAL DELIVERY

Background. Lacerations of the anal sphincter or injury to sphincter i nnervation during childbirth are major causes of fecal incontinence, b ut the incidence and importance of occult sphincter damage during rout ine vaginal delivery are unknown. We sought to determine the incidence of damage to the anal sphincter and the relation of injury to symptom s, anorectal physiologic function, and the mode of delivery. Methods. We studied 202 consecutive women six weeks before delivery, 150 of the m six weeks after delivery, and 32 with abnormal findings six months a fter delivery. Symptoms of anal incontinence and fecal urgency were as sessed, and anal endosonography, manometry, perineometry, and measurem ent of the terminal motor latency of the pudendal nerves were performe d. Results. Ten of the 79 primiparous women (13 percent) and 11 of the 48 multiparous women (23 percent) who delivered vaginally had anal in continence or fecal urgency when studied six weeks after delivery. Twe nty-eight of the 79 primiparous women (35 percent) had a sphincter def ect on endosonography at six weeks; the defect persisted in all 22 wom en studied at six months. Of the 48 multiparous women, 19 (40 percent) had a sphincter defect before delivery and 21 (44 percent) afterward. None of the 23 women who underwent cesarean section had a new sphinct er defect after delivery. Eight of the 10 women who underwent forceps delivery had sphincter defects, but none of the 5 women who underwent vacuum extractions had such defects. Internal-sphincter defects were a ssociated with a significantly lower mean (+/-SD) resting anal pressur e (61+/-11 vs. 48+/-10 mm Hg, P<0.001) six weeks post partum, and exte rnal-sphincter defects were associated with a significantly lower sque eze pressure (increase above resting pressure, 70+/-38 vs. 44+/-13 mm Hg; P<0.001). There was a strong association (P<0.001) between sphinct er defects and the development of bowel symptoms. Conclusions. Occult sphincter defects are common after vaginal delivery, especially forcep s delivery, and are often associated with disturbance of bowel functio n.