The impact of vitamin D on pregnancy: a systematic review.

Hypovitaminosis D is common in pregnancy. To systematically review the evidence on vitamin D-dependent pregnancy outcomes, PubMed and Embase were searched for randomized control trials, cohort and case-control studies. In randomized control trials ( n = 7), larger doses of vitamin D resulted in higher 25-hydroxylated vitamin D (25OHD) levels ( n = 6), increased maternal weight gain ( n = 1), and fewer classical vitamin D deficiency symptoms ( n = 1). In observational studies ( n = 32), lower vitamin D intake, or low 25OHD-levels, were associated with adverse fertility parameters ( n = 2), preeclampsia ( n = 5), gestational diabetes or higher blood glucose ( n = 6), bacterial vaginosis ( n = 4), primary cesarean section ( n = 1), none ( n = 3) or a few days' ( n = 2) shorter gestation, and postpartum depression ( n = 1). Studies with few participants having low 25OHD did not identify an association to preeclampsia ( n = 5) or gestational diabetes ( n = 2). Increased odds of pregnancy-associated breast cancer with 25OHD >25.8 nmol/L were observed ( n = 1). In conclusion, an effect of vitamin D on several pregnancy outcomes is suggested. [ABSTRACT FROM AUTHOR]