90. Early prenatal use of a multivitamin diminishes the risk for inadequate vitamin D status in pregnant women: results from the Maternal-Infant Research on Environmental Chemicals (MIREC) cohort study (lay summary)

Weiler H,  Brooks SPJ, Sarafin K, Fisher M, Massarelli I, Luong TM, Johnson M, Morisset AS, Dodds L, Taback S, Helewa M, Von Dadelszen P, Smith G, Lanphear BP, Fraser WD, Arbuckle TE. American Journal of Clinical Nutrition 2021 Jun 3:nqab172. doi: 10.1093/ajcn/nqab172

Vitamin D plays a number of important roles during pregnancy for the mother and growing fetus.  The best way to know if a person has enough vitamin D is to measure blood levels of a form of vitamin D called 25-hydroxyvitamin D [25OHD]. Researchers at Health Canada undertook this study to measure 25OHD levels in early and late pregnancy to learn if women get enough vitamin D from food and supplements.

Pregnant women enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) study took part in this study. Prenatal 25OHD concentrations were measured during the first trimester, third trimester, and at delivery. Researchers used statistical models to analyze determine the percentage of women with adequate 25OHD concentrations.  Adequate concentrations are defined as greater than or equal to 40 nmol/L.

Women’s 25OHD concentrations increased from the first to the third trimester and decreased a small amount from the third trimester to delivery.  The majority of women had adequate levels of 25OHD at each time point. Women who did not take a multivitamin were less likely to have adequate vitamin D levels than those who took a daily multivitamin. Women who had already been pregnant and women whose household income was below average were less likely to take a multivitamin.

This study demonstrates that that multivitamins are an effective way to get an adequate amount of vitamin D during pregnancy. Future research will investigate the associations between 25OHD levels and risks of pregnancy complications.