Gestational diabetes mellitus has been described as a transient form of diabetes caused by insulin resistance and pancreatic β-cell dysfunction during pregnancy, which first occurs or is first diagnosed in pregnancy. Diabetes in pregnancy significantly endangers the mother's health by increasing the risk of developing preeclampsia, then by damaging endothelial cells predisposes the mother to the development of cardiovascular diseases and increases the risk of developing type 2 diabetes later in life. The fetus may develop macrosomia during pregnancy, followed by respiratory distress syndrome and postpartum hypoglycemia. Macrosomia is defined as a fetal weight greater than 4000 g or 4500 g, regardless of gestational age. Risk factors for macrosomia need to be identified on time so that they can be influenced. Currently, fetal weight is estimated using biometric parameters (biparietal diameter, abdominal circumference, head circumference, femur length) measured by ultrasound, but the accuracy of the estimate decreases with an increase in fetal weight greater than 4000 g. The most commonly used formulas for fetal weight assessment are Hadlock and Shepard, together with about 30 other formulas. However, none is precise enough in the case of the development of macrosomia. An accurate diagnosis of macrosomia can only be made by measuring weight after birth. Prevention of complications of macrosomia is carried out by diagnosis and treatment of gestational diabetes mellitus.