Interventions to increase physical activity in pregnancy are challenging for morbidly obese women. Targeting sedentary behaviors may be a suitable alternative to increase energy expenditure. We aimed to determine total energy expenditure, and energy expended in sedentary activities in morbidly obese and lean pregnant women. We administered the Pregnancy Physical Activity Questionnaire (nonobjective) and the Actical accelerometer (objective) to morbidly obese (BMI ≥ 40 kg/m²) and lean (BMI ≤ 25 Kg/m²) pregnant women recruited in early (<24 weeks), and late (≥24 weeks) gestation. Data are mean (SD). Morbidly obese pregnant women reported expending significantly more energy per day in early (n = 140 vs 109; 3198.4 (1847.1) vs 1972.3 (10284.8) Kcal/d, P