Gestational diabetes mellitus (GDM) is associated with both short- and long-term adverse outcomes in mothers. Included among these adverse outcomes is a long-term risk of developing type 2 diabetes. One of the questions addressed in the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) Follow-Up Study (FUS) is whether mothers diagnosed with GDM using the International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria had a similar risk 10-14 years following the HAPO pregnancy. GDM diagnosed using IADPSG criteria was associated with a 3.4-fold higher risk of developing a disorder of glucose metabolism (type 2 diabetes, impaired fasting glucose, impaired glucose tolerance) compared to women with normal glucose tolerance during pregnancy. Despite the high risk of developing a disorder of glucose metabolism following a diagnosis of GDM, postpartum follow-up of women with a history of GDM is often inadequate despite explicit recommendations for follow-up from the American Diabetes Association and other groups. Developing approaches during pregnancy for identifying women at highest risk for progression to a disorder of glucose metabolism could enhance postpartum follow-up. To address this, we used targeted metabolomics in the HAPO FUS cohort to further characterize metabolic changes at 28 weeks gestation associated with GDM. GDM was associated with broad-based metabolic changes similar those seen in type 2 diabetes. Circulating metabolites at 28 weeks gestation were also associated with maternal glucose levels and/or development of a disorder of glucose metabolism 10-14 years after the HAPO pregnancy. However, inclusion of metabolite levels at 28 weeks gestation together with maternal clinical factors did not improve prediction of development of a disorder of glucose metabolism beyond using clinical factors alone. Mediation analyses did demonstrate that a core group of metabolites at 28 weeks gestation associated with postpartum maternal glycemic traits mediated, in part, the association of GDM with development of a disorder of glucose metabolism. In summary, women with GDM diagnosed using IADPSG criteria are at risk for developing a disorder of glucose metabolism, and while metabolomics did not improve models for predicting progression to a disorder of glucose metabolism, it has helped to define the underlying pathophysiology of this process.