Diabetes mellitus is a multifaceted, chronic disease that happens either when the pancreas does not produce enough insulin or when the human body cannot competently use the insulin it produces. The study was aimed to determine and show the ultrastructural changes of cells in the placenta of women suffering from diabetes mellitus disease. In this study, a total of 102 placentas were investigated by transmission electron microscopy, which includes 34 placentas with gestational diabetes, 34 placentas with pregestational diabetes, and 34 placentas with normal pregnancy as a control group. Placental vascular-syncytial membrane, trophoblastic basement membrane, villous stroma, and fetal vessel were investigated for their thickening basement membrane, edema, glycogen deposition, and any other abnormality and scored as Ns-no significant change, - absent, + mild, ++moderate, +++severe. The study of the central section in the placentae of two diabetic women groups revealed a decrease in the thickness of the vascular-syncytial membrane and density of syncytiotrophoblast apical microvilli and increased thickness of trophoblastic basement membrane, glycogen deposits, and edema. The study concluded that the placental ultrastructural abnormalities are higher present in diabetic women, especially in the pregestational diabetes group