Factors affecting newborn bone mineral content: in utero effects on newborn bone mineralization

Several factors have been found recently to have a significant impact on ne wborn bone mineral content (BMC) and developing fetal bone. Recently we sho wed that maternal vitamin D deficiency may affect fetal bone mineralization . Korean winter-born newborn infants had extremely low serum 25-hydroxyvita min D (25-OHD), high serum cross-linked carboxy-terminal telopeptide of typ e I collagen (ICTP; a bone resorption marker), and markedly lower (8 %) tot al body BMC than summer-born newborn infants. Infant total body BMC was pos itively correlated with cord serum 25-OHD and inversely correlated with ICT P, which was also negatively correlated with vitamin D status. In three sep arate studies on North American neonates we found markedly lower (8-12 %) B MC in summer newborn infants compared with winter newborn infants, the oppo site of the findings for Korean neonates. The major reason for the conflict ing BMC results might be the markedly different maternal vitamin D status o f the North American and Korean subjects. Recently, we found evidence of de creased bone formation rates in infants who were small-for-gestational age (SGA) compared with infants who were appropriate-for-gestational age; we re ported reduced BMC, cord serum osteocalcin (a marker of bone formation) and 1,25-dihydroxyvitamin D (the active metabolite of vitamin D), but no alter ations in indices of fetal bone collagen metabolism. In theory, reduced ute ro-placental blood flow in SGA infants may result in reduced transplacental mineral supply and reduced fetal bone formation. Infants of diabetic mothe rs (IDM) have low BMC at birth, and infant BMC correlated inversely with po or control of diabetes in the mother, specifically first trimester maternal mean capillary blood glucose concentration, implying that factors early in pregnancy might have an effect on fetal BMC. The low BMC in IDM may be rel ated to the decreased transplacental mineral transfer. Cord serum ICTP conc entrations were higher in IDM than in control subjects, implying increased intrauterine bone resorption. BMC is consistently increased with increasing body weight and length in infants. Race and gender differences in BMC appe ar in early life, but not at birth. Ethanol consumption and smoking by the mother during pregnancy affect fetal skeletal development.