Typical prenatal vitamin D supplement intake does not prevent decrease of plasma 25-hydroxyvitamin D at birth.

Objective: The objective of this longitudinal study was to determine what typical vitamin D predictors influence the change in vitamin D status from mid-pregnancy to birth.Methods: Plasma 25-hydroxyvitamin D [25(OH)D] was determined at mid-pregnancy (8–20 weeks gestation) and following birth (n = 193). Usual predictors of vitamin D status [body mass index (BMI), race, season] in addition to prenatal supplemental vitamin D intake and docosahexaenoic acid (DHA) status at delivery were assessed for their interaction on the change on plasma 25(OH)D concentration between the two time points.Results: Forty-nine percent of women had inadequate vitamin D status [categorized as deficient (<30 nmol/L) or insufficient (30–49.9 nmol/L) by IOM guidelines] at mid-pregnancy and 82% were deficient or insufficient at birth. Plasma 25(OH)D concentration dropped 61% from mid-pregnancy to birth. Season of birth (F = 7.86, P = 0.006) and mid-pregnancy plasma 25(OH)D concentration (F = 6.17, P = 0.014) were significant variabl...