Concentrations of 24,25-dihydroxyvitamin D and 25-hydroxyvitamin D in paired maternal-cord sera.

Mean serum concentrations of 24,25-dihydroxyvitamin D (24,25(OH)2D) and 25-hydroxyvitamin D (25OHD), measured by competitive radioassays, were significantly higher in maternal serum than in cord serum of term infants in both black and white subjects. There were positive correlations between maternal and cord levels of both metabolites of vitamin D. Serum concentrations of 24,25(OH)2D and 25OHD were significantly lower in white pregnant subjects than in nonpregnant women. In utero levels of 24,25(OH)2D and 25OHD probably reflect maternal stores of these metabolites.