 This study aims to serially evaluate liver and visceral fat stores during pregnancy and their relationship with glucose and lipid metabolism, placental function, and newborn size. To do this we will conduct both a prospective cohort study of pregnant women without pre-gestational or early gestational diabetes assessed at both 12-16 weeks gestation and at 32-36 weeks gestation and a case-control study of women with normal and impaired glucose tolerance in the early third trimester. Physical assessments will be performed by the Oregon Health and Science University bio-nutrition unit and will include the use of magnetic resonance imaging, ultrasound, and blood draws. 