The effect of vaginal delivery on the urethral sphincter.

To investigate the aetiological role of vaginal delivery in genuine stress incontinence we compared two groups of women who underwent full urodynamic assessment in our department. The women in the first group had competent urethral sphincter mechanisms and those in the second group had genuine stress incontinence. There were no differences between the two groups in respect of parity, number of vaginal deliveries or birthweight of the heaviest baby. The group with competent urethral sphincter mechanisms did show some evidence to implicate an increased number of vaginal deliveries in poor function of the distal part of the urethral sphincter mechanism.