Effect of second vaginal delivery on anal function in patients at risk of occult anal sphincter injury after first forceps delivery

PURPOSE: The study was designed to determine the effect of further vaginal delivery on anal sphincter function in women after apparently uncomplicated primiparous forceps delivery. METHODS: Fifty-two secundigravid women whose first child was forceps-assisted were compared with a control group of 20 women who had undergone spontaneous first vaginal delivery. Both groups were studied antenatally and again at 12 weeks after second delivery using a standardized bowel function questionnaire, endoanal ultrasound, and anal manometry. The primary outcome was fecal incontinence score after second delivery. RESULTS: Before second delivery, 20 of 52 (39 percent) of the forceps group and 3 of 20 (15 percent) control subjects (P=0.103) reported minor alteration in fecal incontinence. Endoanal ultrasound was more frequently abnormal (38/52 (73 percent) vs. 6/20 (30 percent); P=0.002), and median anal canal squeeze (71 vs. 104 mmHg; P=0.004) and resting pressures (43 vs. 58 mmHg; P=0.004) were lower in the forceps group. There was no difference in continence score between first and second delivery for the forceps group (P=0.19) group or control subjects (P=0.18). However, 10 of 38 (26 percent) women with an abnormal endoanal ultrasound after first forceps delivery developed new or worsening symptoms after second delivery. CONCLUSIONS: One-quarter of women with occult anal sphincter injury after first forceps delivery experienced some minor alteration in fecal continence after the second delivery.