Systematic Review of Placental Changes in Diabetic and Hypertensive Pregnancies: Morphology and Histopathology

Abstract

Background: Diabetes mellitus and hypertensive disorders in pregnancy are significant contributors to maternal and fetal morbidity and mortality worldwide. These conditions are associated with structural and functional alterations in the placenta, which may affect fetal growth, nutrient exchange, and pregnancy outcomes. Understanding the morphological and histopathological changes in placentas from diabetic and hypertensive pregnancies is crucial for improving clinical management and guiding preventive strategies. Objective: To systematically review and synthesize current evidence on placental morphological and histopathological changes in pregnancies complicated by diabetes mellitus and hypertensive disorders. Methods: A comprehensive literature search was conducted across PubMed, Scopus, Web of Science, and Embase for studies published up to 2025. Studies included original research reporting placental morphological or histopathological alterations in diabetic or hypertensive pregnancies. Data extraction focused on study design, population characteristics, placental findings, and relevant clinical outcomes. The quality of included studies was assessed using the Newcastle-Ottawa Scale for observational studies. Results: The review included 42 studies comprising over 3,000 placentas from diabetic and hypertensive pregnancies. Diabetic pregnancies were predominantly associated with placental enlargement, villous immaturity, increased intervillous fibrin deposition, and stromal fibrosis. Hypertensive pregnancies showed increased infarction, syncytial knots, fibrinoid necrosis, and decreased villous vascularity. Some studies reported overlapping features in pregnancies complicated by both diabetes and hypertension, suggesting synergistic pathological effects. Histopathological alterations were often correlated with adverse fetal outcomes, including intrauterine growth restriction, preterm birth, and perinatal complications. Conclusion: Diabetic and hypertensive pregnancies exhibit distinct and overlapping morphological and histopathological placental changes, which are strongly associated with adverse fetal outcomes. Recognition of these alterations can aid in risk stratification, improve monitoring strategies, and provide insights into the pathophysiology of maternal-fetal complications. Further studies integrating molecular and functional assessments are needed to deepen understanding of placental adaptations in these high-risk pregnancies. Keywords: Placenta, Diabetes Mellitus, Hypertensive Disorders of Pregnancy, Histopathology, Morphology, Pregnancy Complications, Systematic Review.