Ultrasonographic evaluation of pelvic floor structure at antepartum and postpartum periods using three-dimensional transperineal ultrasound.

Purpose: To examine the changes in the pelvic floor structure caused by pregnancy and delivery.

Methods: A total of 141 nulliparous women were examined with three-dimensional transperineal ultrasound (3D-TPU) at the 24th and 34th weeks of gestation, 5th day postpartum, and 1 month postpartum. Puborectalis muscle trauma was diagnosed and the area of levator hiatus (ALH) was measured.

Results: One hundred and five normal vaginal deliveries, 19 vacuum/forceps deliveries, and 17 cesarean deliveries were included. In the normal delivery group, the rate of puborectalis muscle trauma was low and showed no significant change between the 24th and 34th weeks of gestation (12.5% vs. 17.2%, p = 0.42). The rate of trauma significantly increased to 70.2% at the 5th day postpartum (p < 0.001). There was no significant difference between the rates at the 5th day postpartum and 1 month postpartum (73.7%, p = 0.60). The same trend was found in the vacuum/forceps group. In the cesarean section group, no significant change was observed throughout pregnancy and postpartum periods. In the normal delivery group, ALH significantly increased between the 24th and 34th week (14.1 ± 2.6 cm vs. 14.6 ± 3.4 cm, p = 0.007). ALH markedly increased to 20.9 ± 4.8 cm at the 5th day postpartum (p < 0.001). ALH at 1 month postpartum decreased to 17.0 ± 4.3 cm (p < 0.001), but did not return to the value at the 24th week (p < 0.001).

Conclusions: Vaginal childbirth results in enlargement of the levator hiatus. Pelvic floor muscles in pregnant women are affected not only by mechanical damage associated with delivery but also by physiologic changes during pregnancy. The effects of pregnancy and delivery on pelvic floor muscles may persist after delivery.