Serum concentrations of vitamin D metabolites in maternal and umbilical cord blood of Libyan and Norwegian women.

: The serum concentrations of the vitamin D metabolites 25-hydroxyvitamin D (25-OHD), 1,25-dihydroxyvitamin D (1,25-(OH)2D) and 24,25-dihydroxyvitamin D (24,25-(OH)2D), and vitamin D binding protein, calcium, phosphate and alkaline phosphatase were determined in 19 grand multiparous Libyan women at delivery, and in the umbilical cord blood of 14 of their babies. The results were compared with similarly collected data from 22 vitamin D-supplemented Norwegian mother-infant pairs. The median 25-OHD and 24,25-(OH)2D concentrations were significantly lower for the Libyan group (maternal 25-OHD: 34 vs 112 nmol/l; cord 25-OHD: 20 vs 76 nmol/l; maternal 24,25-(OH)2D: 0.6 vs 4.1 nmol/l; cord 24,25-(OH)2D: 0.4 vs 2.7 nmol/l, P less than 0.001 for all differences). In both groups the 25-OHD and 24,25-(OH)2D levels in maternal as well as in cord blood were closely associated (P less than 0.001). The median 1,25-(OH)2D level was similar for the two maternal groups (198 vs 194 pmol/l), but slightly lower for the Libyan than for the Norwegian cord samples (80 vs 93 pmol/l, P = 0.04). A calculated free 1,25-(OH)2D concentration (not bound to vitamin D binding protein) did not differ between the two maternal or cord groups. Calcium and phosphate concentrations were similar for the respective maternal and cord samples, while the median alkaline phosphatase level of cord blood was slightly higher for the Libyan group (P = 0.04). The results suggest that calcium and phosphate homoeostasis of pregnant women and their fetuses can be maintained despite wide variations in vitamin D supply and numerous repeated pregnancies.(ABSTRACT TRUNCATED AT 250 WORDS)