分析各种二胎分娩方式对盆底肛提肌裂孔的影响。

选取在杭州市妇产科医院2018年3月至2019年2月生产的二胎产妇1606例，在产后42 d至2个月进行产后经会阴盆底三维超声检查，测量静息状态下以及最大Vasalva动作后肛提肌裂孔面积。根据2次妊娠分娩方式分为4组，均为经阴道分娩的为组1（1006例），均为剖宫产的为组2（485例），一胎为剖宫产二胎为经阴道分娩的为组3（19例），一胎为经阴道分娩二胎为剖宫产的为组4（96例）。采用多样本秩和检验比较4组静息状态、最大Vasalva动作后以及增大的肛提肌裂孔面积的差异，采用线性回归调整其他因素干扰，分析二胎分娩方式对研究结局的影响。

4组产妇静息状态时肛提肌裂孔面积差异具有统计学意义（H=92.32，P＜0.001），静息状态的肛提肌裂孔面积中组3最大（14.80 cm²）；4组间两两对比Vasalva动作后肛提肌裂孔面积［组1 vs 组2 vs 组3 vs 组4：18.32（25.62，21.70）cm² vs 15.10（12.58，17.99）cm² vs 21.79（16.80，21.33）cm² vs 16.76（13.40，20.39）cm²］，差异均有统计学意义（组1 vs 组2：Z=12.934，P＜0.001；组1 vs 组3：Z=-2.030，P=0.042；组1 vs 组4：Z=-2.958，P=0.003；组2 vs 组3：Z=-4.654，P＜0.001；组2 vs 组4：Z=-3.128，P=0.002；组3 vs 组4：Z=-2.802，P=0.005），4组Vasalva动作后肛提肌裂孔面积增大值比较，差异具有统计学（H=121.15，P＜0.001），一胎为剖宫产二胎为经阴道分娩的产妇（组3）的肛提肌裂孔面积增大值最大（5.76 cm²），二胎均经阴道分娩的产妇（组1）增大值次之（5.44 cm²），二胎均为剖宫产（组2）的增大值最小（3.32 cm²）。二胎剖宫产与顺产相比，静息状态肛提肌裂孔面积缩小1.22 cm²，差异具有统计学意义（t=-4.681，P＜0.001）；Vasalva动作后肛提肌裂孔面积缩小2.10 cm²；差异具有统计学意义（t=-4.432，P＜0.001）；肛提肌裂孔面积增大值缩小0.86 cm²，差异具有统计学意义（t=-2.446，P=0.015）。

在二胎产妇中，一胎剖宫产二胎为经阴道分娩产妇的肛提肌裂孔面积最大，二胎均经阴道分娩的产妇次之，同时最大Vasalva动作后的肛提肌裂孔面积是评价肛提肌裂孔的最佳指标。

To analyse the effects of the mode of delivery on the pelvic floor of the area of levator ani muscle hiatus in women after a second delivery.

A total of 1606 parturients who had a second delivery at Hangzhou Women's Hospital from March 2018 to February 2019 were subjected to postpartum translabial pelvic floor three-dimensional ultrasound examination from 42-60 days post-delivery to measure the levator ani muscle hiatus area at resting time and after maximum Valsalva maneuver. The patients were divided into four groups according to the mode of first and second delivery. Group 1 (1006 cases) had two vaginal deliveries, group 2 (485 cases) underwent two cesarean sections, group 3 (19 cases) had the first cesarean section and the second vaginal delivery, and group 4 (96 cases) had the first child delivered by vagina and second by cesarean section. Kruskal-Wallis H test was used to compare the differences of levator ani hiatus area at resting state, that after Valsalva maneuver, and enlarged levator ani hiatus area among the four groups. Linear regression was used to adjust the interference of other factors, and the influence of delivery mode on the study outcome was analyzed.

Among the four groups, the area of the levator ani muscle hiatus of woman at rest was statistically different (H=92.32, P＜0.001), and it was the largest in group 3 (14.80 cm²). The levator ani hiatus areas after Valsalva maneuver in groups 1-4 were 18.32 (25.62, 21.70) cm², 15.10 (12.58, 17.99) cm², 21.79 (16.80, 21.33)cm², and16.76 (13.40, 20.39) cm², respectively; pairwise comparisons showed a statistically significant difference between group 1 and group 2 (Z=12.934, P＜0.001), group 1 and group 3 (Z=-2.030, P=0.042), group 1 and group 4 (Z=-2.958, P=0.003), group 2 and group 3 (Z=-4.654, P＜0.001), group 2 and group 4 (Z=-3.128, P=0.002), and group 3 and group 4 (Z=-2.802, P=0.005). The increase in the area of levator ani muscle hiatus after Valsalva maneuver was statistically different among the four groups (H=121.15, P＜0.001). The increased area of the levator ani muscle hiatus was the largest (5.76 cm²) in group 3, followed by group 1 (5.44 cm²), and the smallest in group 2 (3.32 cm²). Compared with normal delivery, the area of the levator ani hiatus was significantly reduced by 1.22 cm² at the resting state (t=-4.681, P＜0.001) and by 2.10 cm² after Valsalva operation (t=-4.432, P＜0.001); the increase in the area of the levator ani muscle hiatus decreased by 0.86 cm², and the difference was statistically significant (t=-2.446, P=0.015).

The area of the levator ani hiatus is the largest in women with the first cesarean section and the second vaginal delivery, followed by women who have two vaginal deliveries. The area of the levator ani hiatus after Valsalva maneuver is the best indicator for evaluating levator ani hiatus.