Anal sphincter injury during vaginal delivery--an argument for cesarean section on request?

Fear of damage to the pelvic floor from vaginal delivery and long-term sequelae (urinary and anal incontinence) sometimes being cited as an indication for cesarean section on request. The aim of the present study was to compare the effects of vaginal delivery versus elective cesarean section on anal sphincter function.

We studied 71 consecutive women six weeks before delivery, 52 of them 4-6 weeks after delivery, and all patients with occult sphincter lesions 3 months after delivery. A bowel function questionnaire was completed, and anal endosonography, manometry, and measurement of the pudendal-nerve terminal motor latency were performed.

Forty-two (80.8 percent) patients were delivered vaginally, ten (19.2 percent) by elective cesarean section at term. Clinically recognized anal sphincter injuries occurred in 9.5 percent (4) of patients, two of them developed incontinence for gas. The overall incidence of anal incontinence after vaginal delivery was 4.8 percent. Occult sphincter defects were identified endosonographically in 19 percent (8) of women, there was no reported case of any anal incontinence 3 months after delivery. No woman delivered by cesarean section had altered anal continence or any significant change in anal pressures, rectal sensibility, and PNTML.

Severe sphincter tear is the single most important factor leading to anal incontinence in women, whereas occult sphincter defects are rarely associated with short-term sequelae, but may predispose to the development of anal incontinence later on in life. Elective cesarean section should be recommended for women at increased risk for anal incontinence.