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.