Methods and Procedures: The investigators will test these hypotheses by using clinical metabolism studies (infusion of stable isotope labeled fatty acid, serial blood and breath sampling, and mass spectrometry) to quantify whole-body fat (fatty acid oxidation, lipolysis, and serum fatty acid , triglycerides, VLDL-cholesterol levels) metabolism in 25 diabetic women during the 3rd trimester of pregnancy, and compare these lipid metabolism kinetics to 25 body mass index matched healthy non-diabetic women during pregnancy and determine if alterations in maternal lipid metabolism predict abnormal neonatal heart function in children born to these women.