The dynamic characteristics of the circumvaginal muscles.

Circumvaginal muscle (CVM) maximum pressure was studied as related to the postpartal period, parity, type of birth, episiotomy, age, breastfeeding, physical activity, body mass, stress urinary incontinence, and orgasm in a sample of 98 healthy postpartal and nonpostpartal women. Circumvaginal muscle pressure tracings were obtained from these women using a pressure-sensitive, intravaginal balloon device. Correlations between circumvaginal muscle maximum pressures and episiotomy, age, breastfeeding, physical activity, body mass, stress urinary incontinence, and orgasm were either not significant or only weakly significant. However, Duncan's multiple range test showed differences in the maximum pressures between groups (nulliparous, parity greater than 0, cesarean delivery, and vaginal delivery) and indicated that vaginal birth has a marked weakening effect on the circumvaginal muscles.