Obstetric damage and faecal incontinence.

Anal incontinence for gas or faeces affects up to 11% of adults, and occurs frequently in 2%. The commonest cause in healthy women is unrecognised damage to the anal sphincter during childbirth; 13% of women having their first vaginal delivery develop incontinence or urgency, and 30% have structural changes shown by anal endosonography. The commonest predisposing cause of damage is the use of forceps. When a third-degree tear occurs, 85% of women have persistent structural sphincter defects and 50% remain symptomatic despite primary repair after delivery. Structural damage associated with childbirth is more important than neurological factors. The characterisation of this sphincter damage has led to improved treatment, including successful surgical repair.