The major goal of our proposed study is to validate a new approach to estimating insulin sensitivity and ß-cell function in African-American women compared to non-Hispanic white women in southern Louisiana who are at a high risk for gestational diabetes mellitus (GDM). We will determine whether the whole body insulin sensitivity index (WBISI) and insulinogenic index (IGI) [derived from an oral glucose tolerance test (OGTT)] can be used during 24-28 weeks of pregnancy to accurately estimate the degree of insulin resistance relative to ß-cell function in women with GDM in those with impaired glucose tolerance (IGT) as well as those who are glucose tolerant. Fasting values will also be assessed using the homeostasis model assessment (HOMA-IR and HOMA-%B) to evaluate insulin resistance and ß-cell function. We will explore the potential use of these measures to define the metabolic risk profile of these pregnant women and compare them with obstetric outcomes. We will determine if there are differences in risk that vary by race. Second, given the high likelihood that women who manifest GDM will develop type 2 diabetes mellitus (DM), identification of these patients by ethnic group or other independent determinants will permit intervention after delivery that might delay or prevent the onset of type 2 DM.