Umbilical cord levels of sclerostin, placental weight, and birth weight are predictors of total bone mineral content in neonates.

CONTEXT: During pregnancy, changes occur in the maternal calcium homeostasis to fulfill fetal demand. We hypothesized that the fibroblast growth factor 23 (FGF23) system and Wnt signaling pathway are important for normal skeletal development in the offspring.

AIMS: Circulating α-klotho, FGF23, sclerostin, and 25-hydroxyvitamin D (25(OH)D) at the fetal and maternal sides of the placenta were measured to investigate associations with newborn bone mass independent of maternal BMI, calcium and phosphate levels, placental weight, and birth weight.

METHODS

In a prospective cohort of healthy pregnant women, the total body bone mineral content (BMC) in 202 newborns was measured by dual-energy X-ray absorptiometry. Maternal circulating levels of the biomarkers were measured at gestational weeks 30-32 and in umbilical cord plasma (UCP) at birth.

RESULTS

Mean α-klotho and sclerostin concentrations in the UCP were significantly higher than maternal levels (3004 vs 1077  pg/ml; P<0.001 and 629 vs 346  pg/ml; P<0.001 respectively), and mean 25(OH)D was lower (31 vs 45  nmol/l; P<0.001). The UCP and maternal FGF23 levels were similar. No significant effects of maternal biomarkers on BMC were found in regression analyses. Among UCP biomarkers, only UCP sclerostin was significantly associated with BMC in univariate analyses, and the effect remained significant after adjustment for birth weight and other confounders.

CONCLUSIONS

We found that UCP sclerostin levels, birth weight, and placental weight were significant predictors of neonatal BMC but found no evidence for a main role of maternal levels of α-klotho, FGF23, sclerostin, or 25(OH)D nor of UCP levels of α-klotho, FGF23, or 25(OH)D.