Background: In the United States, there are approximately 1.2 million children born to women with diabetes mellitus (DM) each year. This number is increasing due to the epidemic of type 2 diabetes and obesity in Western society. Infants born to diabetic women (IBDW) have alterations in cardiac morphology and function, which may predispose them to long-term adverse cardiovascular health. At present, mechanisms for adverse cardiovascular outcomes in IBDW are unknown. Abnormal maternal glucose metabolism in DM during pregnancy was previously thought to affect fetal cardiac development. However, recent findings indicate that IBDW with good 3rd trimester glucose control still develop cardiac abnormalities. In fact, other aspects of maternal nutrient metabolism and partitioning (other than glycemic control) may regulate fetal cardiac development. For example, abnormal fatty acid, triglyceride, and lipoprotein metabolism are common in DM, and maternal serum lipid levels in pregnant diabetics predict neonatal birth weight. The investigators propose that maternal fatty acid metabolism is dysregulated in diabetic pregnancy. This increases fatty acid delivery to the fetus and leads to fetal myocardial lipid accumulation, and altered neonatal heart morphology and function in IBDW. To date, this has not been explored in humans. The proposal stems from the "lipotoxicity" paradigm: chronic elevations in maternal blood lipid (i.e. fatty acid, triglyceride, very low density lipoprotein) levels during pregnancy lead to increased lipid delivery to and cause myocardial lipid deposition in the developing fetus. These lipids displace glucose utilization by the fetal myocardium; the preferred fetal heart substrate in a healthy pregnancy. Abnormal fetal heart lipid deposition and accumulation of lipid metabolic intermediates (e.g. ceramide) may lead to myocardial insulin resistance and contractile dysfunction in IBDW. The relationship between abnormal nutrient metabolism during pregnancy and adverse cardiovascular and metabolic health in diabetes may be important in other conditions such as childhood obesity in which this project could provide insight.