This chapter describes causes of stillbirth in diabetic pregnancies. Global prevalence of pregestational diabetes and gestational diabetes has increased in both high-income and low-income group countries. Both pregestational (type I and II) and gestational diabetes contribute to perinatal mortality rate (PNMR). This chapter covers the maternal hyperglycemia and stillbirth, fetal erythropoietin and stillbirth, fetal cardiac dysfunction and stillbirth, and oxidative stress and stillbirth. Maternal hyperglycemia results in fetal hyperglycemia, which stimulates fetal pancreatic β-cells leading to marked fetal hyperinsulinemia. Oxidative stress either by increased generation of free radicals or by inadequate antioxidant defense can lead to abnormal cardiac remodeling, hypertrophic cardiomyopathy, and fetal death.