Umbilical cord osteocalcin in normal pregnancies and pregnancies complicated by fetal growth retardation or diabetes mellitus.

A homologous radioimmunoassay for human osteocalcin was used to measure cord serum osteocalcin concentrations in normal pregnancies and in pregnancies complicated by intrauterine growth retardation (IUGR) and diabetes. The mean osteocalcin concentrations in term newborns (100-110 micrograms/l) were comparable with levels that we previously measured in pubertal children. There was a small increase in mean osteocalcin concentrations during the third trimester of fetal life, with the maximum at 35 weeks; between weeks 36 and 41, the osteocalcin levels dropped by 13%. Osteocalcin was 20% lower in IUGR neonates than in age- or weight-matched newborns. The newborns of diabetic mothers had markedly lower osteocalcin concentrations than the weight-matched neonates, and 16 of the 19 samples were more than 1 SD below the mean of the gestational-age osteocalcin regression curve. Cord serum osteocalcin appears to be a useful parameter in studying normal and abnormal fetal mineralization.