The placenta is the organ situated between the mother and fetus. It plays critical roles during pregnancy and is essential for fetal growth and development. The placental functions are determined by the ultrastructure of the placental barrier which is an exchange surface area between the fetus and mother. Gestational diabetes mellitus (GDM) comprises unfit conditions for embryonic and feto-placental development and may result in placental abnormalities. This study was made to detect the ultrastructural changes of the placenta in women with gestational diabetes. The placentas of 10 control and 10 women with GDM were studied. Whole thickness placental samples were taken and prepared for light and transmission electron microscopy study. Light microscopic study of the control placenta showed numerous densely packed microvilli, thin walled blood vessels and narrow intervillous spaces. The placentas of GDM showed reduced number of microvilli, wide intervillous spaces, thick walled vessels, edematous spaces and areas of fibrosis and perivillous fibrinoid degeneration. Electron microscopic study of the placentas of control women showed terminal villi with a thick layer of syncytiotrophoblast (Sy) with a lot of cylindrical microvilli and a thin layer of cytotrophoblast (Cy). There were some endoplasmic reticulum cisternae beside few mitochondria. The underling villus core was harboring fetal capillaries lined with flat endothelial cells and thin basement membrane. In GDM placenta, there was hypertrophy of Cy with atrophy of the Sy with multiple vacuoles and areas for glycogen storage. The microvilli were scarce and the villous core showed congested capillaries, edematous spaces, glycogen storage areas and fibrosis. All the changes in placentas of GDM are suggested to be attributed to the associated hypoxia and oxidative stress due to the associated decreased uteroplacental flow that was aggravated by the thick placental barrier.
