Anal sphincter injury after vaginal delivery in primiparous females

The purpose of this study was to determine the incidence of anal sphincter injury and fecal incontinence after vaginal delivery.

This was a prospective, descriptive, observational study conducted over a three-year period in healthy primiparous females with previously intact anal sphincter and normal continence and without history of anorectal surgery. All patients completed a continence questionnaire and underwent endoanal ultrasound four to six weeks before and six weeks after delivery.

Ninety-eight primiparous females had either instrumental (vacuum or forceps) vaginal delivery (n = 23) or noninstrumental vaginal delivery (n = 75). Twenty patients, 11 (48 percent) after instrumental delivery and 9 (12 percent) after noninstrumental vaginal delivery, had clinical sphincter tears that required primary repair. Twenty-eight patients (29 percent), 19 with previously repaired sphincter injury, had ultrasonographic defects that involved the external sphincter (n = 19) or both the internal and external sphincter (n = 9). Twenty-one patients (75 percent) with ultrasonographic sphincter defects had either major (n = 5) or minor (n = 16) fecal incontinence.

Anal sphincter injuries, many of them undiagnosed at the time of delivery, are common in primiparous females after vaginal delivery, especially if vacuum or forceps are used. These injuries cause fecal incontinence in a significant proportion of the patients. Patients undergoing vaginal delivery should be aware of the risks of anal sphincter injury.