Participants will complete the following at 12-16 weeks gestation and again at 32-36 weeks gestation:

1. Fasting glucose, insulin and insulin sensitivity testing;
2. Blood tests for cholesterol and fatty acids, liver function, inflammation, and markers of metabolism;
3. Measurements of body fat using air displacement technology and MRI;
4. Ultrasound to measure placental blood flow, visceral fat thickness (12-16 weeks only) and to estimate fetal weight (32-36 weeks only);
5. 24 hour diet recalls
6. Questionaires regarding activity level

Participants diagnosed with gestational diabetes (cases) and without gestational diabetes (controls) will complete the following at 32-36 weeks gestation:

1. Fasting glucose, insulin and insulin sensitivity testing;
2. Blood tests for cholesterol and fatty acids, liver function, inflammation, and markers of metabolism;
3. Measurements of body fat by using air displacement technology and MRI;
4. Ultrasound to measure placental blood flow and to estimate fetal weight;
5. 24 hour diet recalls
6. Questionaires regarding activity level

We will compare visceral adipose fat and intrahepatic lipid levels in early pregnancy (12-16 weeks gestation) to late pregnancy (32-36 weeks gestation). This will done by comparing changes in accumulation of fat in the visceral adipose tissue, changes in intrahepatic lipid values and changes in total body fat in early and late pregnancy. We will be collecting body composition measurements and utilizing ultrasound and Magnetic Resonance Imaging.

We will use a matched case-control design with matching for body mass index to compare intrahepatic lipid, visceral adipose tissue, total body fat, and insulin sensitivity among women with gestational diabetes and normal glucose tolerance, as measured at 32-36 weeks gestation.