['To examine the relationship between physical activity during pregnancy and fasting plasma insulin measured in the second trimester.', 'We conducted a pilot prospective cohort study of 69 overweight or obese women who were enrolled before 20 weeks of gestation at an obstetric clinic in Columbia, South Carolina in 2006-2007. At 24-28 weeks of gestation, fasting blood samples were collected and physical activity from the 3 months prior to the visit was assessed using a validated Pregnancy Physical Activity Questionnaire.', 'Total energy expenditure (EE) in this population was attributable to sedentary activities (24.4%) and to physical activities of different intensities (light: 44.8%, moderate: 30.2%, and vigorous: 0.6%). By type, total EE mainly came from household/caregiving activities (58.9%) with a small proportion from exercise (3.8%). After adjusting for confounders, the mean fasting insulin values across the quartiles of total EE (least to most) were 17.3, 13.0, 12.1, and 9.6 uIU/ml (P for trend=0.01).'] Is physical activity during pregnancy associated with reduced fasting insulin -- the Pilot Pregnancy and Active Living Study?