Regular maternal physical activity leads to the delivery of lighter, leaner infants. Higher birth weights and childhood obesity are both strong predictors for adult obesity, suggesting that the impact of maternal physical activity on the future health of a child is substantial. However, the mechanisms underlying the relationships between maternal physical activity and improved infant outcomes are unclear. Thus, the purpose of this project is to measure two potential contributing factors: maternal fat metabolism and maternal oxidative stress profiles. The investigators believe that maternal physical activity leads to beneficial alterations in maternal fat metabolism and oxidative stress profiles. Further, the investigators believe that both maternal fat metabolism and oxidative stress levels are related to infant outcomes such as obesity and insulin resistance. Therefore, exercise will improve maternal metabolic factors that can lead to improvements in infant outcomes. The investigators will compare these factors between obese inactive pregnant women and obese active pregnant women. This study design will allow us not only to determine the effect of physical activity on maternal and neonatal pregnancy outcomes, but also to establish whether obesity or physical inactivity should be a primary area of focus when prescribing pregnancy interventions in clinical practice.