Gestational diabetes mellitus (GDM) is a serious pregnancy complication in which a woman who has never had diabetes develops chronic hyperglycemia during her pregnancy. Normal placental function is essential for optimal fetal growth. The transport of glucose from the mother to the fetus is critical for fetal nutrient demands and can be stored as glycogen in the placenta. However, the function of this glycogen deposition is unknown: It may well be a source of fuel for a placenta itself or the storage reservoir for the later use by the fetus in times of need. While the significance of the placental glycogen remains unknown, the mounting evidence indicates that the altered glycogen metabolism and/or deposition is associated with many pregnancy complications, such as gestational diabetes, that adversely affect fetal development. The aim of this study is to assess glycogen deposition using Histochemical staining of Periodic Acid Schiff (PAS) stain. The placenta tissue collected from 50 women were enrolled in this study (25 women with no complications) and (25 women with gestational diabetes). The placentas of the two groups were compared in this study based on glycogen deposition with periodic acid-Schiff stain. The results of a histochemical investigation using PAS stain revealed a significant increase in the glycogen deposition (p≤0.001) in diabetic women's placentas within the intervillous core, around fetal vessels, and the basement membranes.