Vitamin D insufficiency, preterm delivery and preeclampsia in women with type 1 diabetes - an observational study

INTRODUCTION: The aim was to evaluate whether vitamin D insufficiency is associated with preterm delivery and preeclampsia in women with type 1 diabetes.

MATERIAL AND METHODS: An observational study of 198 pregnant women with type 1 diabetes. 25-Hydroxy-Vitamin D and HbA1c were measured in blood samples in early (median 8 weeks, range 5-14) and late (34 weeks, 32-36) pregnancy. Kidney involvement (microalbuminuria or nephropathy) at inclusion, smoking status at inclusion, preterm delivery (<37 weeks) and preeclampsia (blood pressure ≥140/90 mmHg and proteinuria) were registered. Vitamin D supplementation of 10 μg daily was routinely recommended.

RESULTS: Thirty-nine (20%) of the 198 women delivered preterm and 16 (8%) developed preeclampsia. Vitamin D insufficiency (< 50 nmol/l) was present in 68 women (34%) in early pregnancy and in 73 women (37%) in late pregnancy. Preterm delivery occurred more frequently in women with vitamin D insufficiency in late pregnancy (27% vs. 15%, crude OR 2.1 (95% CI=1.0-4.3, p=0.04). After adjustment for pre-existing kidney involvement, HbA1c in late pregnancy and smoking the association became non-significant (adjusted OR 1.8 (0.8-3.7)). Preeclampsia developed in 11% of women with vitamin D insufficiency vs. 6% of the remaining women (crude OR 1.8 (0.9-4.1, p=0.25)).

CONCLUSION: In women with type 1 diabetes, preterm delivery was twice as frequent in women with vitamin D insufficiency in late pregnancy in crude analysis, but in this small study, low vitamin D was not independently associated with preterm birth or preeclampsia. This article is protected by copyright. All rights reserved.