Gestational Diabetes Mellitus: The Dual Risk of Small and Large for Gestational Age: A Narrative Review.

Background/Objectives: Gestational diabetes mellitus (GDM) complicates approximately 14% of pregnancies worldwide, its prevalence rising with increasing maternal age and obesity. While maternal hyperglycemia is traditionally associated with fetal overgrowth and large-for-gestational-age (LGA) neonates, emerging evidence indicates that GDM may also contribute to small-for-gestational-age (SGA) outcomes. Methods: A comprehensive literature search was conducted using multiple databases, including PubMed, Web of Science, and ScienceDirect, to identify studies related to gestational diabetes mellitus, fetal growth outcomes such as small for gestational age and large for gestational age, and associated pathophysiological mechanisms. Results: This narrative review explores the mechanisms by which GDM influences fetal growth, emphasizing the dual risk of excessive and restricted intrauterine growth. Fetal macrosomia typically results from chronic maternal hyperglycemia, leading to increased transplacental glucose delivery and fetal hyperinsulinemia. In contrast, SGA outcomes are a consequence of vascular and endothelial dysfunction, placental insufficiency, or excessively restrictive glycemic control that limit the availability of nutrients. Both extremes of fetal growth carry a myriad of significant perinatal and long-term metabolic risks. Conclusions: Understanding the diverse pathways through which GDM affects fetal growth is essential for developing individualized clinical strategies.