Pelvic floor structural changes during the first singleton pregnancy and the risk factors of stress urinary incontinence

Abstract

Background

Pelvic floor dysfunction (PFD) usually occurs due to issues with the pelvic floor muscle and fascia tissue. Although many studies have shown that vaginal childbirth is a risk factor, little is known about the effects of pregnancy. Stress urinary incontinence (SUI) is a common symptom of PFD, characterized by involuntary urine discharge when abdominal pressure increase, such as sneezing, coughing, laughing or exercising. We aimed to observe pelvic floor ultrasound parameters during pregnancy and assess the association with SUI.

Methods

Pregnant participants were recruited from the Affiliated Obstetrics and Gynecology Hospital of Tongji University between March 2022 and December 2023. We assessed pelvic floor anatomy with three-dimensional ultrasound and administered standardized questionnaires to all participants. After conducting the assessments, we saved the volumetric data sets for standardized analysis.

Results

A total of 385 pregnant women were included, with 131 in the first trimester group; 122 in the second trimester group, and 132 in the third trimester group. SUI occurred 7 cases (5.34%) in the first trimester group, 26 cases (23.31%) in the second trimester group, and 63 cases (47.72%) in the third trimester group, the incidence of SUI in different groups with statistically significant (P < 0.001). As the pregnancy advanced, there were significant differences in HA, hiatal anteroposterior diameter, transverse diameter at rest, PFMC and VM (P<0.05). There were significant differences in hiatal transverse diameter at PFMC in the third trimester between women with SUI and those without (P = 0.048). However, no differences were observed in ultrasonic pelvic floor parameters in the first trimester between women with SUI and those without (P>0.05). We performed logistics regression analysis to evaluate the likelihood of SUI, the model was statistically significant (P < 0.001, AUC = 0.778, 95%cl: 0.729–0.827). Our analysis identified BMI, hiatal area at rest, hiatal anteroposterior diameter at rest, and hiatal anteroposterior diameter at VM as independent risk factors for SUI.

Conclusions

Pelvic floor structure begin to change during pregnancy, as the pregnancy advanced, the hiatal area increased gradually.