Objective: The objective of this study is to analyze the alteration in vascularization and apoptosis in the placentas of patients with Type 1 or gestational diabetes mellitus.Methods: Placental samples drawn from normal (n=6), GDM (n=6), and Type 1DM (n=6) pregnancies were rinsed in PBS and fixed in 4% paraformaldehyde. The obtained sections were examined by both light and electron microscopy. Subsequently, immunohistochemical staining was performed to evaluate apoptosis and vascularization with caspase-9 and VEGF antibodies.Results: Capillary structures in various sizes, both in free and in stem villi, were observed to be denser in the GDM group than in the control and Type-1DM groups, utilizing electron microscopy. Similarly, when compared with Type-1DM and controls, a decreased amount of microvilli with more irregularity and blunting on the villus surface was detected. GDM group showed increased immunoreactivity in capillaries of stem villi, free villi, and endothelial cells when compared with Type-1DM and control groups. Regarding the immunohistochemical staining with VEGF, Type-1DM, and GDM groups showed stronger immunoreactivity than the control group, especially in syncytiotrophoblastic cell nuclei and stromal cell nuclei. However, there was no significant difference between Type-1DM and GDM groups.Conclusion: Type-1DM and GDM placentas showed increased villous stromal capillarization, increased immunoreactivity with VEGF and caspase-9, and increased syncytial nodes, which may develop secondary to placental hypoxia-ischemia. However, more participants are needed to confirm these conclusions.