OBJECTIVE--To assess the impact of physical activity on the gestational age at delivery in women performing physical tasks in their jobs during pregnancy. METHODS--Qualified nurses at 15 weeks of pregnancy were asked through a questionnaire to describe the tasks in their regular job, the physical activities involved, and their exposure to other occupational stressors. The physical activities to be identified were walking, standing, lifting, stooping, squatting, and sitting. RESULTS--A high degree of daily physical work load during pregnancy seemed to be a significant predictor for the gestational age at delivery, whereas chemical and infectious agents were not. CONCLUSIONS--Physical work load during pregnancy should be diminished to avoid adverse effects on gestational age at delivery.