Longitudinal Assessment of Vitamin D Across Pregnancy in a Sample from the National Children's Study

Vitamin D deficiency in pregnant women can lead to adverse health outcomes for the mother and her offspring. A circulating 25-hydroxyvitamin D (25(OH)D) cutoff of 20 ng/mL indicates vitamin D adequacy for most healthy individuals, although pregnancy may affect circulating biomarkers. To address this gap, we examined markers of vitamin D (total 25(OH)D, vitamin D binding protein [VDBP], and free 25(OH)D) at three timepoints during pregnancy (1st half [<25 weeks] and 2nd half of pregnancy [≥25 weeks], and birth) among a sub-sample participating in the National Children’s Study (NCS). The sub-sample included an equal number of participants by pre-pregnancy BMI (50% healthy weight [18.5 ≥BMI<25 kg/m2] and 50% overweight/obese [BMI≥25kg/m2]). The results will characterize changes in vitamin D metabolites across pregnancy and provide preliminary data for the clinical utility of measuring free 25(OH)D, over total 25(OH)D, as an indicator of vitamin D status during pregnancy.