Effect of vaginal delivery on endosonographic anal sphincter morphology

To describe the effect of vaginal delivery with no clinically recognized sphincter tear on endosonographic anal sphincter morphology and sphincter pressure and to relate endosonographic results to anal sphincter pressure and anal incontinence score.

Thirty-two nullipara underwent anal endosonography and anal manometry in the third trimester of pregnancy, 2 weeks and 6 months post-partum. The sphincter defect scores (1-16) and the thickness and length of the sphincters were measured by endosonography, and sphincter pressures and manometric sphincter lengths were determined. The Wexner incontinence score (1-20) was used to classify anal incontinence 6 months post-partum.

Five (16%) women had small endosonographic anal sphincter defects (score 3-4) before delivery. Eight women (25%; confidence interval 11-43%) had new defects detected post-partum, five small, one moderate (score 7), and two large (score 10-11). Six (75%) of eight women with new defects post-partum had undergone episiotomy versus five (21%) of 24 women with no new defects (p = 0.02). Six months after delivery 16 (50%) women reported anal incontinence, and there was a positive correlation between the endosonographic defect score 6 months post-partum and the Wexner incontinence score. The sphincter was significantly longer during pregnancy than 6 months post-partum.

New sphincter defects may arise after vaginal delivery without any clinically recognizable sphincter tear. There is a positive correlation between the endosonographic defect score 6 months post-partum and the Wexner incontinence score.