Introduction: Gestational diabetes mellitus is defined as any degree of glucose intolerance with onset or first recognition during pregnancy. This condition is associated with an increase of important outcomes in the fetus and newborn. Objectives: Review of gestational diabetes mellitus physiopathology and the metabolic/hormonal changes that happen in the fetal environment. Review of the impact in the mother, intrauterine environment, fetus and newborn. Results: The maternal metabolic disorders, particularly the hyperglycemia, increase the the risk of intrauterine and neonatal morbidity. This includes macrosomia (large for gestational age), neonatal hypoglycemia, hyperbilirubinemia, hypocalcemia, polycythemia and respiratory pathology. Gestacional diabetes mellitus is also associated with an increased frequency of maternal hypertensive disorders, eclampsia and hydramnios which represent as well, potential risk for the fetal development. The intensive metabolic management is required in order to prevent all these outcomes which include also intrauterine death and prematurity. Women with gestacional diabetes mellitus are at increased risk for the development of diabetes, usually type 2, after pregnancy. Offspring of women with gestacional diabetes mellitus are at increased risk of obesity, glucose intolerance,and diabetes in late adolescence and young adulthood. Conclusion: Gestacional diabetes mellitus is a disease with a complex management although the tight glycemic control is consensually regarded to improve its prognostic. In consequence it is essential to improve the knowledge about the metabolic modifications in the intrauterine environment and its consequences.