Statistical Analysis: Repeated measures ANOVA (group x time) will be used to compare lipid oxidation rates and oxidative stress profiles between the 2 groups during pregnancy before, during, and after exercise. Pearson product moment correlation coefficients for normally distributed variables and Spearmen's rank order coefficients for non-normally distributed variables will be used to examine the relationships between maternal lipid oxidation rate, plasma oxidative stress markers, and neonatal metabolic outcomes. We may also use a regression analysis to examine the relationship between maternal physical activity levels in obese women and neonatal body composition and/or insulin resistance (similar to what has been done in normal weight pregnant women by Pomeroy et al. 2012).