Effect of pregnancy on anal sphincter morphology and function.

Twenty pregnant women were investigated prospectively to establish if pregnancy had any effect on the function and morphology of the anal sphincters. Anal endosonography and manometry were performed during pregnancy and 6 weeks after Caesarean section. Muscle thickness of the puborectalis, longitudinal muscle, internal and external anal sphincter were measured. There was no significant difference in the muscle thickness of either before and after Caesarean delivery. The maximum resting pressure and the maximum squeeze pressure were not significantly changed. No significant correlation was found between anal pressure and muscle thickness of either sphincter. Pregnancy itself does not have a significant effect on anal sphincter morphology or function. Any changes in sphincter function that occur in relation to pregnancy or delivery are likely to be due to mechanical trauma rather than hormonal changes in pregnancy.