Vitamin D in pregnancy: current concepts

Abstract

Purpose of review: Vitamin D is part of a complex steroid hormone system long known to be involved in bone metabolism. Recently, vitamin D has been implicated in physiologic processes as diverse as vascular health, immune function, metabolism and placental function. This review summarizes the current evidence for the role of vitamin D in pregnancy and perinatal outcomes A systematic review of articles published in PubMed between May 2010 and October 2011 was undertaken using key words for vitamin D and pregnancy. Seventy-eight studies were reviewed.

Recent findings: The biologic evidence regarding a role for vitamin D in reproductive outcomes is strong, and rates of vitamin D deficiency may be high among pregnant women. However, no consensus exists regarding optimum vitamin D levels in pregnancy or standard measurement of vitamin D deficiency. Clinical studies establishing an association between vitamin D levels and adverse pregnancy outcomes such as preeclampsia, gestational diabetes, low birthweight, preterm labor, cesarean delivery and infectious diseases have conflicting results. This is likely due to a paucity of randomized trials, heterogeneity of populations studied and low sample size with poor adjustment for confounding among observational studies.

Summary: Further research should focus on defining optimum 25-hydroxy vitamin D levels in pregnancy as well as among various subgroups of the population. Randomized trials are needed to determine whether vitamin D supplementation can improve pregnancy outcomes. Currently, the American College of Obstetrics and Gynecology and the Institute of Medicine recommend 600 IU of daily vitamin D supplementation during pregnancy to support maternal and fetal bone metabolism.

Figures

Figure 1

Vitamin D metabolism and tissue actions. 25(OH)D, 25-hydroxy vitamin D; Ca2+, calcium; CRP, C-reactive protein; DBP, vitamin D binding protein; DM, diabetes mellitus; MMP9, matrix metalloproteinase 9; PO4, phosphate; PTH, parathyroid hormone; SGA, small for gestational age; UVB, ultraviolet B.