Calcium (ca),Phosphorus( P) and 25-hydroxyvitamin D(25OHD)] in Infants Born ≤ 32 PMA Gestational Weeks (GA)

It has not yet been established the optimal dose of vit. D for preterm infants in Poland. It is not known what dose of vit. D will provide the correct concentration of vit. D and the optimal development of the skeleton of the premature. The study will try to determine the optimal supplementation of vitamin D and the supply of Ca and P for normal growth and development of a child born prematurely. In addition, the investigators will evaluate any risk factors for deficiency and excess of vitamin D and the consequences of its deficiency and overdose. Simultaneously the study would make possible the determination of an optimal schedule for controlling the Ca-P levels in the group of the youngest infants born prematurely. In addition, the study will assess the relationship between maternal and newborn vitamin D resources right after birth, and the incidence of vitamin D deficiency in infants born prematurely. Preterm infants will be randomized in 3 groups assigned to different doses of vit. D. The study will investigate the metabolism of calcium, phosphorus, the health of bones and development of the premature babies till the age of 2.