The natural history of clinically unrecognized anal sphincter tears over 10 years after first vaginal delivery.

Objective: To estimate the influence of clinically unrecognized anal sphincter injuries detected by endoanal ultrasonography 3 months after first vaginal delivery on symptoms of anal incontinence over the subsequent 10-year period.

Methods: One-hundred fifty-six consecutive primigravid women were recruited, anal endosonography performed, and bowel habit predelivery characterized by means of a validated 24-point questionnaire. After excluding four women with a clinically recognized sphincter tear after delivery and 18 who delivered by cesarean, these procedures were repeated 3 months postpartum.