Maternal Serum 25-Hydroxyvitamin D and Measures of Newborn and Placental Weight in a U.S. Multicenter Cohort Study

Context: Inconsistent associations between maternal vitamin D status and fetal size have been published in small studies. Objective: Our objective was to examine the association between maternal 25-hydroxyvitamin D [25(OH) D] levels and measures of newborn and placental weight. Design and Setting: We measured maternal 25(OH) D in mothers from the Collaborative Perinatal Project, an observational cohort conducted in 12 U. S. medical centers from 1959 to 1965. Participants: Women delivering singleton, term, live births with 25(OH) D measured at a gestation of 26 wk or less (n = 2146). Main Outcome Measures: Birth weight, ponderal index, placental weight, the placental to fetal weight ratio, andsmall for gestational ageweremeasured. Hypotheseswereformulated after data collection. Results: After confounder adjustment, mothers with 25(OH) D of 37.5 nmol/liter or greater gave birth to newborns with 46 g [95% confidence interval (CI), 9-82 g] higher birth weights and 0.13 cm (0.01-0.25 cm) larger head circumferences compared with mothers with less than 37.5 nmol/liter. Birth weight and head circumference rose with increasing 25(OH) D up to 37.5 nmol/liter and then leveled off (P < 0.05). No association was observed between 25(OH) D and ponderal index, placental weight, or the placental to fetal weight ratio. Maternal 25(OH) D of 37.5 nmol/liter or greater vs. less than 37.5 nmol/liter in the first trimester was associated with half the risk of small for gestational age (adjusted odds ratio 0.5; 95% CI 0.3-0.9), but no second-trimester association was observed. Conclusions: Maternal vitamin D status is independently associated with markers of physiological and pathological growth in term infants. Adequately powered randomized controlled trials are needed to test whether maternal vitamin D supplementation may improve fetal growth. (J Clin Endocrinol Metab 98: 398-404, 2013)