Diabetic pregnancy represents the most important challenge of insulin therapy, requiring a continuous effort to maintain euglycemia and avoid severe hypoglycemic episodes. Hypoglycemia becomes a charge nearly inevitable to pay. Pregnancy itself may be associated with impaired counter-regulation system and hypoglycemia unawareness. The risk of hypoglycemia in diabetic pregnancy is mainly due to the pharmacokinetics of current therapies that produces inappropriately high insulin concentrations and a failure in the physiological protective mechanism that limits falls in blood glucose concentrations. Around 45-71% of type 1 diabetic women experienced severe hypoglycemia during pregnancy; severe hypoglycemia can occur during pregnancy 3-5 times more frequently in the first trimester and at a lower rate in the third trimester. Risk factors include a history of severe hypoglycemia in the preceding years, long duration of diabetes, low hemoglobin A1c in early pregnancy, fluctuating plasma glucose levels, and excessive use of supplementary insulin between meals and impaired hypoglycemia awareness. The effects of hypoglycemia on the fetus is controversial, in particular its possible role in teratogenicity is still debated. Low levels of maternal glucose during pregnancy may cause fetal growth retardation and small for gestational age infants. In addition, maternal hypoglycemia may also determine impaired fetal beta cell function.