Perinatal bone turnover in term human neonates and the influence of maternal smoking

Bone turnover in neonates appears independently of the comparably low maternal bone turnover, but there is only sparse information on the effect of the in utero environment on fetal bone turnover. Postnatally, the resuming growth velocity and alterations in mineral homeostasis affect neonatal bone turnover. This study evaluated the relationship of bone marker concentrations to maternal and fetal auxological variables as well as maternal smoking and assessed the short-term change in bone markers during the first days of life. Serum markers of bone formation [osteocalcin and bone-specific alkaline phosphatase (BALP)] and bone resorption (C-terminal telopeptide of type I collagen) were measured in cord blood and at discharge (median d 3) in 69 healthy term neonates. Concentrations of BALP were significantly lower in neonates of smokers (n = 16) compared with nonsmokers (n = 53), both at birth (p = 0.013) and at discharge (p = 0.036). Both cord osteocalcin and BALP were negatively related to maternal weight and maternal body mass index. Maternal smoking and pregnancy weight gain were the predictors of cord BALP (r2 = 0.24; p < 0.001), whereas the mode of delivery best predicted cord C-terminal telopeptide of type I collagen levels (r2 = 0.19; p < 0.001). C-terminal telopeptide of type I collagen and osteocalcin increased significantly (p < 0.001) from birth to discharge, whereas BALP levels did not change significantly during the same period. Our results suggest that maternal smoking during pregnancy and maternal obesity may have a negative impact on fetal bone formation. The significant increase of osteocalcin and C-terminal telopeptide of type I collagen may result either from an increase in bone turnover or altered renal clearance.