Vitamin D is important for the development, growth, and mineralization of the skeletal in neonates and children. Vitamin D is essential for intestinal absorption of calcium. Vitamin D is metabolized to 25-hydroxyvitamin D and then to 1,25-dihydroxyvitamin D. Pregnant women in developed countries often have insufficient serum concentrations of 25-hydroxyvitamin D and a supplementation of vitamin D is necessary, usually a daily dose of 400 IU of vitamin D is sufficient to increase the serum level of 25-hydroxyvitamin D to normal value of >75nmol/l. Supplementation of vitamin D increases birth weight and birth length compared to newborn infants born to unsupplemented pregnant women. Oral vitamin D3 (35,000 IU per week) increases total serum calcium in cord blood. This dose, during the third trimester of pregnancy, enhances early postnatal linear growth. Mean change in length from birth to 1 month was significantly greater in vitamin D supplemented pregnant women versus placebo (p=0.0004). At 1 year, mean in length was 1.1 cm longer in infants born to mothers supplemented with vitamin D compared to infants born to mothers unsupplemented with vitamin D. The head circumference is lower in vitamin D deficiency newborns. Vitamin D deficiency during childhood is associated with an increased risk of skeletal disorders and vascular abnormalities. Respiratory distress syndrome is more common in severely vitamin D deficient preterms and supplementation with vitamin D to the mothers reduces respiratory distress syndrome in neonates. The aim of this study is to review the effects of vitamin D in neonates.