The aim was to assess associations between urinary incontinence (UI) and Vitamin D insufficiency in mid-pregnancy.

This is a secondary analysis of a randomized controlled trial including 855 healthy pregnant women recruited in pregnancy week 18-22. Blood samples were collected after an overnight fasting, and the sera were stored at -80 °C. The analysis of 25-hydroxyvitamin D [25(OH)D] levels was performed on stored sera. Serum 25(OH)D levels <50 nmol/L were classified as Vitamin D insufficiency. Questionnaires regarding prevalence of UI (Sandvik’s severity index) were completed. Urinary leakage was classified according to the definitions given in the standardised IUGA/ICS terminology of lower urinary tract symptoms. Women confirming any type of urinary leakage were referred to as having UI, and women reporting leakage with activities increasing abdominal pressure were referred to as having stress urinary incontinence (SUI).

Complete data on level of Vitamin D and UI were available for 823 women. Mean age was 30.5 years, and 57% were nulliparous. Vitamin D insufficiency was found in one third of women. More women with Vitamin D insufficiency reported UI (49% vs. 39%, p<0.01) and SUI (36% vs.25%, p=0.001) compared to women with adequate Vitamin D status.

Vitamin D insufficiency is prevalent in pregnancy, and has been related to adverse health effects. The presence of Vitamin D receptors in both striated muscle of the pelvic floor and bladder smooth muscle  and the findings in the present study suggests that Vitamin D exert influence in the development of UI. Future studies may evaluate the impact of Vitamin D supplementation on UI.

The present findings indicate a possible association between Vitamin D insufficiency and incident UI in otherwise healthy pregnant women.