Pelvic floor biometry in Chinese primiparous women 1 year after delivery: a prospective observational study

To evaluate pelvic floor biometry in Chinese women 1 year following childbirth and to explore factors that affect it.

Translabial ultrasound examination was performed at rest, on Valsalva maneuver (VM) and on pelvic floor muscle contraction (PFMC) in the first, second and third trimesters of pregnancy and at 8 weeks, 6 months and 12 months after delivery in a cohort of women delivering at term their first child. Offline analysis was undertaken to measure the position of the bladder neck, cervix, anorectal junction and hiatal dimensions at each posture and at each visit, and to detect levator ani muscle (LAM) injury on PFMC 8 weeks and 12 months after delivery. Results were analyzed according to mode of delivery.

We recruited 442 women, of whom 328 (74.2%) completed the study; there was LAM injury in 48 women at 8 weeks and in only 38 women at 12 months. When comparing first-trimester biometry to that at 12 months after delivery, the bladder neck was more distal on VM and bladder neck displacement was increased, and the cervix was lower at rest and on VM in the vaginal delivery group. In the Cesarean section group, bladder neck and anorectal junction were more distal on VM, the cervix was lower at rest, on VM and on PFMC, and the hiatal area was increased on VM. There was a greater increase in hiatal area after vaginal delivery. Overall, 34.8% had irreversible hiatal distension (> 20% increase in hiatal area after delivery as compared to first trimester). LAM injury was significantly associated with irreversible hiatal distension (odds ratios, 5.2-9.5 at different postures).

Pregnancy beyond 35 weeks of gestation has an effect on the pelvic floor of Chinese women, irrespective of mode of delivery. The pelvic organs remain more mobile after delivery when compared to in the first trimester, and there is no clear difference between the findings observed following vaginal delivery or Cesarean section, except in hiatal distension, which is greater after vaginal delivery. LAM injury is the factor most strongly associated with irreversible hiatal distension.