Mild gestational diabetes: towards a redefined threshold?

Gestational diabetes mellitus (GDM), the most common medical complication of pregnancy, is defined as carbohydrate intolerance resulting in hyperglycemia of variable severity with onset or first recognition during pregnancy. In reality, gestational diabetes mellitus is a spectrum of maternal hyperglycemia caused or exacerbated by pregnancy, in which blood glucose levels lie along a continuum, associated with a wide spectrum of metabolic abnormalities and conferring varying degrees of pregnancy-related risk. In recent years, the WHO diagnostic thresholds in current use have been called into question, as increasing evidence mounts that 'mild gestational diabetes' confers increased maternal and fetal risk, despite glucose levels falling below current thresholds. This review summarizes the existing evidence, unanswered questions and health service implications related to women with so-called 'mild' gestational diabetes.