In order to be able to say gestational diabetes, the symptoms of diabetes must have appeared during pregnancy. Steroid hormones during pregnancy develop resistance to insulin hormone, which lowers blood sugar. For this reason, all pregnant women should go through the screening of sugar at 24-28 weeks of gestation. Known risk factors for the development of gestational diabetes are the overweight of the expectant mother, having a history of diabetes before, having previously delivered an overweight baby, and a history of giving birth to a dead baby before. Recent studies suggest that vitamin D deficiency causes gestational diabetes in mothers. Measurement of serum 25 hydroxy vitamin D yields the most accurate result. Pregnancy does not increase the need for vit D. The daily intake is 600 IU / day. The 25 hydroxyvitamin D level should be 50 nmol / L (20 ng / ml). Vitamin D tends to decrease during pregnancy and during the postpartum period. This situation creates some conditions for both the mother and the baby. The vit D store of the newborn depends on the mother. 25 hydroxyvitamin D in mother blood and cord blood is linked. Vitamin D that your mother will take will increase this. In the mother, vitamin D regulates insulin cells in the pancreas. Both the amount of insulin carried by glucose increases, as well as the amount of insulin increases. 25 levels of hydroxyvitamin D in gestational diabetic patients were found to be below normal. In cases with HOMA index (insulin resistance) above 3, vitamin D deficiency is more common.