All women who seek pre-natal care at the Women's Health Clinic at Barnes Jewish Hospital/Washington University will be screened for inclusion BMI by history at the clinic. Subjects will be recruited late in their 2nd trimester at the women's health clinic after asking about their exercise habits. All patients who meet criterion with on-going pregnancies will be approached for enrollment in the study. This study will compare 2 groups of pregnant women between 30 and 35 weeks gestation. The first group will inactive obese women and the other will be active obese women. We will recruit ~15 subjects per group (N=30). Groups will be race-matched.