The aim of the proposed study is to examine the relationship of occupational and leisure time physical activity to birth weight. Increasing numbers of pregnant women are continuing to work and engage in exercise up until the time of delivery. Epidemiologic data on lifestyle factors and pregnancy, except for effects of alcohol consumption and cigarette smoking, are scant. The effects of occupational and leisure time physical activity will be examined in 250 women who deliver at Magee Womens Hospital in Pittsburg. The women will be identified using clinic and private obstetricians' schedule records. Questionnaires will be administered prospectively during a first, second and third trimester prenatal visit. It is believed that this study has the potential to advance our understanding of the relationship of occupational and leisure time activity during preganancy to birth weight, and to provide suggestions for the formulation of recommended levels of occupational and leisure time activity during pregnancy.