Levator function before and after childbirth

Vaginal childbirth is assumed to affect pelvic floor muscle function as a result of direct trauma and/or neuropathy.

To assess levator function by ultrasound prior to and after delivery and correlate changes with delivery data.

A total of 200 nulliparous women were seen at 6-18 and 32-37 weeks' gestation as well as 2-5 months post-partum. Appointments consisted of an interview, paper towel test, flowmetry and translabial ultrasound (supine and after voiding). The most effective of at least three contractions was used for evaluation according to a previously published method quantifying cranioventral displacement of the bladder neck. Labour and delivery details were collected through data collection sheets and the institutional database.

A total of 173 women were seen in late pregnancy; 169 returned on average 93 days post-partum. At the last visit, a reduction of cranioventral lift from 11.2 mm (SD 4.5) to 8.8 mm (SD 4.2) was noted (P <0.001) which correlated weakly with active second stage (Spearman's r=-0.196, P=0.013), passive second stage (r=-0.15, P=0.059) and total second stage of labour (r=-0.225, P=0.004). Good antenatal levator function was not protective of changes in levator function or pelvic organ support.

Childbirth reduces bladder neck displacement on levator contraction. The main obstetric determinant affecting levator function seems to be the length of the second stage. A Caesarean section in the second stage appears to exert no protective effect. It seems to be full engagement of the fetal head, not childbirth itself, that impairs levator function.