Vitamin D and stress urinary incontinence in pregnancy: a cross-sectional study.

OBJECTIVE To assess the association between levels of vitamin D and urinary incontinence (UI) in pregnancy. DESIGN A cross-sectional study. Secondary analysis of a randomised controlled trial. Setting Two university hospitals in Norway. Population 851 healthy, pregnant women >18 years in gestational week 18-22 with a singleton live fetus. METHODS Data on UI were collected from a questionnaire at inclusion and serum analysis of 25-hydroxy vitamin D (25(OH)D) was performed. Univariable and multivariable logistic regression analyses were applied to study associations between exposure and outcomes. Main Outcome Measures Prevalence of self-reported UI, stress (SUI) and urge (UUI) or mixed UI. RESULTS In total 230/851 (27%) of the participants were vitamin D insufficient (25(OH)D <50nmol/L) and 42% reported to have any UI. Women with 25(OH)D <50nmol/L were more likely to report any UI (p=0.03) and SUI (p<0.01) compared to women with 25(OH)D ≥50nmol/L. In a univariable logistic regression analysis, serum levels of 25(OH)D <50nmol/L was associated with increased risk of any UI (Odds Ratio, OR 1.5 with 95% Confidence interval CI (1.0, 2.1)), SUI only (OR 1.7 (1.2, 2.4)), but not mixed UI or UUI only (OR 0.8 (0.5,1.5)). In a multivariable logistic regression model, serum levels of 25(OH)D <50nmol/L was associated with a higher risk of experiencing SUI only (OR 1.5 (1.1,2.2)). CONCLUSIONS Serum 25(OH)D <50nmol/L was associated with increased risk of any UI and SUI in particular.