Transperineal combined two- and three-dimensional ultrasound evaluation of the effects of different delivery methods on levator ani muscles and pelvic organ prolapse.

Background: The levator ani muscle (LAM) comprises the main component of female pelvic floor support structure and plays an important role in maintaining the normal position of pelvic organs. Early detection of its injury is critical to ensure the health of the pelvic floor. Vaginal delivery exacerbates LAM injury, and LAM injury changes the normal pelvic floor structure. Therefore, this study used ultrasound to measure the degree of pelvic organ decline enabling qualitative assessment of the severity of prolapse. To investigate whether vaginal delivery leads to greater LAM trauma and pelvic organ support loss than does cesarean delivery, we utilized combined two-dimensional (2D) and three-dimensional (3D) ultrasound to better evaluate the changes of pelvic floor structure in different delivery modes. Methods: From December 2021 to October 2023, 130 patients with a full-term singleton pregnancy (weighing 2.50-4.00 kg) who underwent pelvic floor ultrasound examination were divided into a forceps group, a non-forceps group (spontaneous delivery was achieved without the aid of other means), and a cesarean section group. The ultrasound images and clinical data of the three groups were analyzed. 2D and 3D ultrasound of the pelvic floor was used to measure the levator ani-urethral gap (LUG) in a constrictive anal state, the levator ani hiatus area (LHA) in the Valsalva state, the degree of pelvic organ descent, and the degree of LAM injury. The differences between different groups were compared. Chi-square test and one-way analysis of variance (ANOVA) were used to compare whether there were differences among the three groups. Bonferroni correction was performed. Results: The injury degree of LAM in the forceps group, the non-forceps group, and the cesarean section group decreased in turn, and the difference was statistically significant (P<0.001). In the Valsalva state, the lowest points of the anterior and middle pelvic organs in the forceps group and the non-forceps group were farther from the reference line than those in the elective cesarean section group, and the difference was statistically significant (P<0.001). Anterior pelvic prolapse was more severe than middle pelvic prolapse across all delivery groups (the Chi-squared value for anterior pelvic prolapse was 22.919; that for the middle pelvic organs was 14.541). Conclusions: Transperineal 2D combined with 3D ultrasound can effectively evaluate the effects of different delivery modes on the LAM and pelvic floor structure. Vaginal delivery increases the incidence of LAM injury and anterior and middle pelvic prolapse. The use of forceps can aggravate the degree of LAM injury, but it is not a high risk factor for prolapse. Pregnancy has a more significant effect on anterior pelvic prolapse than it does on middle pelvic prolapse.