Exercise during pregnancy is associated with the delivery of leaner, lighter, and healthier infants (Clapp 1990, Clapp 2000). Subsequently, high infant adiposity and birth weight are strong predictors of childhood obesity and adult adiposity (Catalano 2006, Danielzk 2002). Therefore, maternal physical inactivity during pregnancy may have significant ramifications for the child, the effects of which may extend well into adulthood. Exercise during pregnancy also plays an important role in the health of the mother. Active pregnant women tend to gain less weight during pregnancy (Clapp 1995) and retain less weight following pregnancy (O'Toole, 2003). With excessive gestational weight gain being the strongest risk factor for maternal overweight and obesity postpartum, as well as being associated with many adverse maternal and neonatal metabolic outcomes such as adiposity and insulin resistance (Heerwagen 2010), the impact of exercise on maternal and neonatal outcomes could be substantial. The mechanisms underlying these changes are poorly understood and studies which strive to expose them are critical.