Habitual physical activity in non-gravid individuals has been shown to positively alter lipid metabolism by increasing fatty acid oxidation (Martin 1996), but the effect of physical activity on maternal lipid metabolism during pregnancy has not been studied. Due to previous research suggesting that an altered intrauterine metabolic environment may play a significant role in fetal programming (Heerwagen 2010), it is reasonable to believe improvements in maternal lipid metabolism may contribute to improved neonatal metabolic outcomes in exercising pregnant women. Preliminary data from our group found that in obese and lean pregnant women, lipid oxidation rate was significantly correlated to offspring birth weight; suggesting maternal lipid metabolism may contribute to neonatal metabolic outcomes. In inactive pregnant women, impaired lipid oxidative capacity in conjunction with known increased physiologic adipose tissue lipolysis that occurs during pregnancy and obesity would result in excess un-oxidized plasma fatty acids that are likely to be re-esterified in adipose tissue and/or delivered to the fetus. This series of events may contribute to increased maternal and neonatal adiposity.