Associations Between the Number of Vaginal Delivery and Urinary Incontinence in Women Before and After Natural Menopause: A Cross-Sectional Study.

Purpose: Urinary Incontinence (UI) associates with menopausal status and vaginal delivery (VD). Existing literature has not confirmed a cumulative effect of an increasing number of VDs on UI incidence, while hormonal changes following natural menopause modulate the risk of UI. This study investigate the association between the number of VDs and UI by stratifying women based on menopausal status. Patients and Methods: This study examined the relationship between the number of VDs and categories of UI, including Stress Urinary Incontinence (SUI), Urge Urinary Incontinence (UUI), and Mixed Urinary Incontinence (MUI) in pre- and postmenopausal women, utilizing publically accessible data from the National Health and Nutrition Examination Survey (NHANES, 2007-2018). Weighted multivariable logistic regression, restricted cubic splines (RCS), and subgroup analyses with interaction tests were used to examine their association. Results: This study comprised 4,046 premenopausal and 2,698 postmenopausal women. Adjusted multivariable regression analysis (Model 2) revealed that compared to nulliparous women, the risk of SUI significantly increased with ≥1 VDs in premenopausal women (1 VD: OR=2.53; 2 VDs: OR=3.73; ≥3 VDs: OR=2.94; all P<0.001) and with ≥2 VDs in postmenopausal women (2 VDs: OR=1.52; ≥3 VDs: OR=1.62, all P<0.05). MUI risk was elevated at 2 VD in both premenopausal (OR=1.78, P=0.012) and postmenopausal women (OR=1.57, P=0.049). No significant association was detected between the number of VDs and UUI in either group. RCS modeling revealed inverse U-shaped relationships between the number of VDs and SUI risk and L-shaped relationships with MUI risk across both groups (nonlinear P < 0.001). Conclusion: The number of VDs exhibits positive associations with incident SUI and MUI, while no significant association was detected with UUI. Notably, the additional risk for SUI and MUI associated with the number of VDs was attenuated in postmenopausal women compared to premenopausal women. Prospective studies are warranted to validate the robustness of these associations.