What Is Gestational Diabetes—Really?

Gestational diabetes mellitus (GDM) is not one disease but many that share inadequate β-cell function as a common cause for elevated glucose levels. Inadequate β-cell function may result from factors that occur outside of pregnancy, such as autoimmunity, monogenic disorders, obesity, and insulin resistance. Pregnancy-specific causes may exist as well but remain to be defined. Detailed physiological studies in women with obesity reveal that inadequate β-cell function is likely a chronic condition that is detected by routine glucose screening in pregnancy and that worsens over time, leading to diabetes in later life. The authors' studies in Hispanic patients identify obesity and insulin resistance as important causes of β-cell dysfunction, providing a rationale for treating both to prevent diabetes after GDM. Additional work is needed to define the full breadth of underlying causes of GDM as the basis for precision management during and, especially, after pregnancy.