Pregnancy increases requirements for insulin secretion, increasing insulin resistance and demands on pancreatic b cells, promoting development of gestational diabetes (GD), particularly in women with preexisting insulin resistance, commonly in women with polycystic ovary syndrome. Preliminary studies suggest that metformin may have the unique potential to prevent the development of GD. We postulate that interventions that reduce insulin resistance and lower requirements for endogenous insulin secretion can preserve b-cell function and prevent the development of type 2 diabetes mellitus.