Cholecalciferol (vitamin D3) is a prohormone and its active form is 1,25 dihydroxycholecalciferol. This hormone has effect on both calcium, phosphorus and bone metabolism and also bone morrow, muscle, heart and immune system. For a long time, maternal low vitamin D level is a well known problem for our country and the level was reported as <10 ng/ml for 46-80% of mothers.The most prominent risk factor was determined as low socioeconomic status. Therefore, the level of 25-hydroxy-vitamin D is supposed to be in relation with several neonatal morbidities and maternal complications of pregnancy.