The article presents a review of literature data (sources: Pubmed, Medline, eLibrary) on maternal obesity in gestational diabetes mellitus as a risk factor for diabetic fetopathy. Against the background of obesity during pregnancy, the level of glucose and insulin in the fetus increases, the synthesis of leptin and its secretion by fetal adipocytes increases, which further increases the level of glucose, insulin, leptin and the metabolic response of hypothalamic neurons occurs, followed by the development of macrosomia in the fetus. Diabetic fetopathy can form from 12 weeks with increased glycemia in a woman. Maternal obesity during pregnancy programs important aspects of the energy balance of newborns that make up the risk group for the development of metabolic syndrome and obesity in future patients, which underlies the «fetal origin of adult diseases».