Gestational diabetes mellitus (GDM) is a significant pregnancy complication characterized by chronic hyperglycemia in women without a pre-existing diabetes diagnosis. It is primarily caused by impaired glucose tolerance due to pancreatic β-cell dysfunction and chronic insulin resistance. Risk factors include obesity, advanced maternal age, and a family history of diabetes. Consequences of GDM include increased risks of maternal cardiovascular disease, type 2 diabetes, and birth complications, as well as long-term health issues in the child, such as obesity and metabolic diseases. GDM affects approximately 16.5% of pregnancies globally, with a higher prevalence in low- and middle-income countries. The molecular mechanisms underlying GDM are not fully understood, and there is no widely accepted treatment or prevention strategy. This review discusses the current knowledge of GDM pathophysiology, focusing on β-cell dysfunction, chronic insulin resistance, neurohormonal networks, adipose tissue, liver, muscle, gut microbiome, oxidative stress, and placental transport. Understanding these processes is crucial for developing effective treatments and prevention strategies.Gestational diabetes mellitus (GDM) is a significant pregnancy complication characterized by chronic hyperglycemia in women without a pre-existing diabetes diagnosis. It is primarily caused by impaired glucose tolerance due to pancreatic β-cell dysfunction and chronic insulin resistance. Risk factors include obesity, advanced maternal age, and a family history of diabetes. Consequences of GDM include increased risks of maternal cardiovascular disease, type 2 diabetes, and birth complications, as well as long-term health issues in the child, such as obesity and metabolic diseases. GDM affects approximately 16.5% of pregnancies globally, with a higher prevalence in low- and middle-income countries. The molecular mechanisms underlying GDM are not fully understood, and there is no widely accepted treatment or prevention strategy. This review discusses the current knowledge of GDM pathophysiology, focusing on β-cell dysfunction, chronic insulin resistance, neurohormonal networks, adipose tissue, liver, muscle, gut microbiome, oxidative stress, and placental transport. Understanding these processes is crucial for developing effective treatments and prevention strategies.