Pelvic Floor Muscle Strength in the First Trimester of Primipara: A Cross-Sectional Study

Background: Pelvic floor muscle (PFM) weakness is associated with stress urinary incontinence. Pregnancy is an important risk factor for PFM weakness. Studies evaluating PFM strength in the first trimester of pregnancy are still lacking. Our study aimed to describe pelvic floor function of the primipara in the first trimester of gestation and investigate the risk factors for PFM weakness. Methods: Primiparas aged 20--40 years with a singleton pregnancy less than 14 weeks of gestation were recruited, and data were collected via questionnaires on items that were suggested as associated with PFM weakness, followed by Modified Oxford Scale (MOS) on genital hiatus and perineal body and pelvic floor ultrasound evaluation for the thickness of the left and right levator ani muscles (LAM), right-left diameter of the levator hiatus (LH), and LH area. Participants were divided into three groups by MOS >3, =3, and <3 for data analysis. Results: A total of 380 participants completed the questionnaires and examinational analysis, of whom, 228, 98, and 54 were divided into Group 1, Group 2, and Group 3, respectively. The three groups were significantly different in the number of gestations and abortions, toilet types, and the right-left diameter of the LH (p < 0.05). Logistic regressive analysis showed that squatting toilet dominant (OR = 3.025; 95% CI: 1.623-5.638; p < 0.001) and a larger right-left diameter of the LH (OR = 1.065; 95% CI: 1.026--1.105; p = 0.001) were significantly associated with PFM weakness. Conclusions: Squatting toilet dominancy and longer right-left diameter of the LH are significantly associated with PFM weakness in primiparas in the first trimester. Sitting toilets should be recommended to women, especially pregnant women.