What is gestational diabetes? Gestational diabetes is a condition of varying degrees of high blood sugar that occurs or is first identified during pregnancy, including impaired glucose tolerance and diabetes that were not identified before pregnancy. Gestational diabetes can endanger the health of both the fetus and the mother. The impacts on offspring mainly include an increased risk of fetal mortality in the womb, i.e., an increased risk of complications from congenital abnormalities, an increased risk of macrosomia, and an increased risk of neonatal hypoglycemia and developing diabetes or impaired glucose tolerance during adolescence or young adulthood.