Maternal fitness levels will be assessed using a submaximal cycle test on a recumbent bicycle. Subjects will sit comfortably on the bicycle while the pedals are properly adjusted so there is a slight bend in the knee when legs are extended. They will then complete the YMCA submaximal multistage cycle ergometer test according ACSM's guidelines for exercise testing and prescription (Thompson 2010). Sady and colleagues concluded that the VO2-Heart Rate extrapolation method is the most precise way to predict VO2max in pregnancy (1985)., and the YMCA test utilizes this method. A 3-lead ECG will be applied to monitor heart rate during the exercise test.