Design: Whole-body lipid metabolism kinetics (fatty acid oxidation, lipolytic, clearance rates) will be measured during clinical metabolism studies using stable isotope tracer methodology and mass spectrometry performed in the Clinical Research Unit and Biomedical Mass Spectrometry Facility at Washington University School of Medicine. Umbilical cord blood will be collected at parturition and serum lipid (fatty acid, triglyceride and VLDL) and other nutrient as well as growth-related hormone levels will be quantified. Neonatal heart function (within 2 weeks of parturition) will be examined using 2D, Doppler, tissue Doppler and strain/strain rate echocardiography performed at St. Louis Children's Hospital.