To observe the near-term impact of the second natural delivery on the structure of a female pelvic floor by ultrasonography.

Selected fifty second-natural-delivery women and fifty first-natural-delivery women from Tongde Hospital of Zhejiang Province between October, 2016 and October, 2017 undertook pelvic ultrasonnography (42 days postpartum). Pelvic ultrasonography was used to determine all mothers′ bladder neck descent, bladder posterior angle, bladder neck tilt angle, bladder neck rotation angle, and the area of pelvic diaphragm hiatus when performing the Valsalva maneuver. Besides, pelvic ultrasonography was used to determine the extent of mothers′ internal-urethral-of-orifice funneling, perineal hyperactivity, uterine prolapse and rectal bulge. The paired t test was applied between groups to compare the bladder neck descent, bladder posterior angle, bladder neck tilt angle, bladder neck rotation angle and the area of pelvic diaphragm hiatus of the second-natural-delivery mothers with those of the first-natural-delivery mothers. The χ² test was also applied to examine the degree of mothers′ uterine prolapse, rectal bulge and internal-urethral-of-orifice funneling, as well as their perineal hyperactivity rate.

The bladder neck descent, bladder posterior angle, bladder neck tilt angle, bladder neck rotation angle and the area of pelvic diaphragm hiatus of the second-natural-delivery mothers were all wider than those of the first-natural-delivery mothers [(29.37±5.32) mm vs (22.63±6.35) mm, (148.8±14.97)^° vs (141.2±15.20)^°, (73.69±16.03)^° vs (69.8±15.25)^°, (44.41±19.27)^° vs (40.0±17.52)^°, (21.47±5.19) cm² vs (19.15±4.10) cm²], and differences were statistically significant (t=5.761, P<0.001; t=2.519, P=0.001; t=2.476, P=0.001; t=3.123, P=0.001; t=2.481, P<0.001). The degree of the second-natural-delivery mothers′ uterine prolapse and internal-urethral-of-orifice funneling as well as their perineal hyperactivity rate were all higher than those of the first-natural-delivery mothers [46.0% (23/50) vs 20.0% (10/50), 12.0% (6/50) vs 6.0% (3/50), 20.0% (10/50) vs 6.0% (3/50)], and differences were statistically significant (χ²=7.644, P=0.006; χ²=3.342, P=0.043; χ²=4.332, P=0.037). The differences in the incidence rate of rectal bulge between the two groups were of no statistical significance [4.0% (2/50) vs 2.0% (1/50), χ²=1.197, P=1.000].

The pelvic ultrasonogram showed that the near-term impacts of the second natural-delivery on women′s pelvic floor were more obvious than those of the first natural delivery. What′s more, pelvic floor ultrasound has been proved to be a reliable basis for the diagnosis and screening of dysfunctional diseases of pelvic floor.