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: A total of 851 healthy, pregnant women >18 years in gestational weeks 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 <50 nmol/l) and 42% reported to have any UI. Women with 25(OH)D <50 nmol/l were more likely to report any UI (P = 0.03) and SUI (P < 0.01) compared with women with 25(OH)D ≥50 nmol/l. In a univariable logistic regression analysis, serum levels of 25(OH)D <50 nmol/l was associated with increased risk of any UI (odds ratio [OR] 1.5 with 95% CI 1.0-2.1), SUI only (OR 1.7, 95% CI 1.2-2.4), but not mixed UI or UUI only (OR 0.8, 95% CI 0.5-1.5). In a multivariable logistic regression model, serum levels of 25(OH)D <50 nmol/l were associated with a higher risk of experiencing SUI only (OR 1.5, 95% CI 1.1-2.2).

Conclusions: Serum 25(OH)D <50 nmol/l was associated with increased risk of any UI, and SUI in particular.

Tweetable abstract: Low levels of vitamin D are associated with increased risk of urinary incontinence in pregnancy.