The project objective is to validate a new indirect estimate of insulin status in both pregnant African-American women and Caucasian women in southern Louisiana who are at risk for gestational diabetes mellitus. There are racial differences in carbohydrate metabolism that are potentially linked to complications during pregnancy and to increased risks of obesity and diabetes in later life. The investigators will explore the use of indexes of insulin status to identify the metabolic risk profile of pregnant women which may vary by race. Understanding whether there are differences which vary by race may influence clinical screening and treatment of pregnant women.

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.

Inclusion Criteria:

• 18-42 years of age
• at 20-30 weeks of gestation
• Caucasian or African-American and non-users of medications known to influence carbohydrate metabolism.

Exclusion Criteria:

• <18 years or >42 years of age
• non-Caucasian or non-African-American ethnicity
• use of drugs that could interfere with glucose or insulin metabolism; or health problems such as diabetes mellitus or liver, heart, lung and kidney diseases

Healthy, nondiabetic pregnant African-American and Caucasian women who have been scheduled for a standard 3-hour glucose tolerance test at 24-28 weeks in the Woman's Hospital Pathology laboratory.