Serum Vitamin D and Vitamin D-binding protein levels in mother-neonate pairs during the lactation period

Abstract

Background: To determine longitudinally the relationship between serum 25-hydroxyVitamin D (Vitamin D) and Vitamin D-binding protein (DBP) levels in mother-neonate pairs and evaluate the efficiency of prophylactic Vitamin D on lactation days 45-60. Methods: Mother-neonate pairs whose serum calcium (Ca), phosphorus (P), magnesium (Mg), alkaline phosphatase (ALP), and parathyroid hormone (PTH) levels were in normal ranges on postpartum/postnatal days 5-10 were classified into two groups by their serum Vitamin D concentrations (Group A: < 10 ng/ml and Group B: > 20 ng/ml). Both maternal and neonatal Ca, P, Mg, ALP, and PTH concentrations in group A and B were not different. Maternal and neonatal serum DBP levels were measured in two groups. The mother-neonate pairs in both groups were given 400 IU/d Vitamin D orally. The same biochemical markers in group A were remeasured on days 45-60 of the lactation period. Results: In group A, the mean maternal and neonatal Vitamin D levels on postpartum/postnatal days 5-10 were significantly lower and the DBP levels were significantly higher than those in group B (P = 0.000; P = 0.000 and P = 0.04; P = 0.004, respectively). On lactation days 45-60, the maternal and neonatal DBP concentrations were not different from those on postpartum/postnatal days 5-10. However, the maternal and neonatal Vitamin D levels were significantly increased (P = 0.000 and P = 0.000, respectively), while the neonatal PTH concentrations were significantly decreased (P = 0.000). The maternal and neonatal Vitamin D concentrations were negatively correlated with their DBP concentrations (P = 0.048 and P = 0.002, respectively). Conclusion: High maternal and neonatal DBP levels may lead to an incorrect low estimate of the true Vitamin D concentration. In this case, only prophylactic Vitamin D (400 IU/d) is indicated for mothers and their infants.