- Gestational diabetes mellitus (GDM) is defined as any degree of glucose intolerance with onset or first recognition during pregnancy. The definition of GDM does not preclude the possibility that unrecognized glucose intolerance may have existed before the pregnancy, and the definition applies whether insulin, oral antidiabetic agents, or dietary modification is used for treatment. Approximately 7% of all pregnancies in the United States are complicated by gestational diabetes resulting in more than 200,000 cases annually, but the prevalence ranges from 1% to 14% of all pregnancies depending on the population studied and the diagnostic tests used. Despite the better detection of GDM and recognition of its adverse consequences for mother and baby in many countries, there is still no consensus regarding GDM pathophysiology; as a result, diagnosis and treatment of GDM remain controversial. A better understanding of obesity along with new studies in GDM has identified the intra-abdominal metabolically active adipose tissue as a major factor in the pathophysiology of GDM. This review examines recent research regarding the link between obesity and glucose intolerance and highlights studies in the areas of genetics, glucose transport, and adipokines.