Gestational Diabetes Mellitus

Definition

Gestational Diabetes Mellitus (GDM) is glucose intolerance of variable severity with onset or first recognition during pregnancy, leading to maternal hyperglycemia and potential fetal complications.

Epidemiology

• Occurs in 5–10% of pregnancies worldwide; higher prevalence in South Asian, Hispanic, and African populations.
• Incidence rising due to obesity, advanced maternal age, and sedentary lifestyle.
• Most commonly diagnosed in the second or third trimester (24–28 weeks gestation).
• Risk of developing type 2 diabetes postpartum is increased.
• Recurrence risk in subsequent pregnancies is 30–50%.

Etiology

• Pregnancy-associated insulin resistance due to placental hormones: human placental lactogen, estrogen, progesterone, cortisol, and prolactin.
• Predisposing factors: obesity, family history of diabetes, advanced maternal age, prior GDM, polycystic ovary syndrome.
• Genetic susceptibility (variants in genes related to insulin secretion and action).
• Lifestyle factors: sedentary behavior, poor diet, excessive weight gain in pregnancy.

Pathophysiology

• Pregnancy induces physiological insulin resistance, increasing maternal glucose levels.
• Pancreatic beta-cells may fail to compensate with adequate insulin secretion.
• Hyperglycemia results in increased glucose crossing the placenta.
• Fetal hyperinsulinemia leads to macrosomia and metabolic complications.
• Postpartum, glucose metabolism may normalize, but underlying insulin resistance persists in many women.