Fetal birthweight and maternal urinary incontinence in Chinese primiparas: a population-based study

Urinary incontinence (UI) is commonly linked to pregnancy and obstetric factors, but the association between fetal birthweight and maternal UI remains contentious. This study investigates the association between fetal birthweight and maternal UI and its subtypes in Chinese primiparas.

Cross-sectional data from 54,346 women aged 20 years and above were obtained from the 2019-2021 National Urinary Incontinence Survey. Restricted cubic spline (RCS) regression analysis and threshold effect analysis were used to explore the association between fetal birthweight and urinary incontinence and its subtypes.

Among 19,365 primiparas, the prevalence of UI was 14.5%. Adjusted analyses revealed that each 1.0 kg increase in birthweight correlated with a 32% (95% CI: 1.21-1.44) increased risk of UI. Categorical analysis indicated that women in the highest birthweight tertile (3.4-6.0 kg) faced a higher risk of UI compared to those in the lowest tertile (0.5-3.0 kg) (adjusted OR, 1.42; 95% CI: 1.28-1.57). RCS regression highlighted non-linear associations between birthweight and the risk of any type of UI, urgency UI (UUI), and mixed UI (MUI), with a significant turning point at 3.9 kg for overall UI risk. Subgroup analyses revealed interactions between birthweight tertiles and modifiable risk factors like physical activity, as well as clinical risk factors like hypertension.

These findings underscore the independent association between fetal birthweight and UI in Chinese primiparas, emphasizing the importance of considering various factors when assessing this relationship. A non-linear association exists between birthweight and any type of UI, UUI, and MUI, respectively. This study offers novel insights into the potential classification strategies for fetal birthweight and call for future research to validate and comprehend the clinical implications.