 Calcium and vitamin D homeostasis and skeletal remodeling in the mother will be monitored closely throughout the pregnancy. Bone density of the mother will be measured at 12 weeks gestation and one-month postpartum. Follow-up growth and skeletal integrity assessments of the infant will be performed at birth, 1, 6 and 12 months stratified by infant feeding regime. Through these proposed studies, the prevalence of hypovitaminosis D among mothers, their developing fetuses and neonates, and the utility of maternal therapeutic intervention with vitamin D for both mother and fetusinfant will be assessed. 