OBJECTIVE To evaluate placental abnormalities in pregnancies affected by diabetes compared to unaffected pregnancies from a single academic center. METHODS This is a retrospective cohort study of women with singleton gestations delivered at the University of Arkansas for Medical Sciences from 2007 to 2016. Pathologic examination of placentas from pregestational and gestational diabetic pregnancies were compared to placentas from patients without diabetes using 12 histologic elements. Maternal and neonatal outcomes were extracted from the medical record and compared between groups. Findings were adjusted for hypertensive disorders of pregnancy. Placental lesions were also correlated with diabetic control. RESULTS Pathology reports of 590 placentas along with corresponding medical records were reviewed. The diabetic group (N = 484) consisted of 188 patients with pregestational diabetes and 296 patients with gestational diabetes. The nondiabetic group consisted of 106 patients. The diabetic group was older, had a higher average BMI, and more hypertensive disorders (p < .0001). Out of the 12 histologic elements investigated, accelerated villous maturation (aOR = 8.45, 95%CI (1.13-62.95)) and increased placental weight (aOR = 3.131, 95% CI (1.558-6.293)) were noted to be significantly increased in placentas from diabetic pregnancies after controlling for hypertension. Intervillous thrombi were not significantly increased in pregnancies affected by diabetes. Neonates of the diabetic group were more likely to be large for gestational age (p < .0001) and had a higher rate of preterm delivery (p < .0001). CONCLUSIONS Accelerated villous maturation was found to be more frequent in pregnancies complicated by pregestational diabetes, even after controlling for hypertension. In pregnancies complicated by gestational diabetes, the placental findings were not significant after controlling for hypertension. In contrast with prior studies, there was no increase in thrombotic lesions of the placenta in patients with diabetes.