Placental fibrosis and microvascular dysfunction in gestational diabetes mellitus: histopathological and ultrastructural evidence from a South African cohort.

Gestational diabetes mellitus (GDM) is a pregnancy-associated metabolic disorder characterized by hyperglycemia and chronic low-grade inflammation, both contributing to placental dysfunction. This study investigated placental pathology in a South African cohort. GDM placentas demonstrated increased fibrin deposition and altered villous stromal architecture, consistent with a stressed placental microenvironment. Polarized light microscopy revealed heterogeneous collagen birefringence patterns, indicating disrupted extracellular matrix organization with a shift in type I and type III collagen balance, consistent with progressive fibrotic remodeling and impaired microvascular integrity. Ultrastructural examination revealed thickened basement membranes and mitochondrial degeneration, indicative of microangiopathic injury and oxidative stress-related cellular damage. These findings demonstrate coordinated histopathological and ultrastructural placental remodeling in GDM involving inflammation, fibrosis, and microvascular dysfunction.