OBJECTIVE: To study a possible association between physical activity and the duration of second stage of labor among Hispanic women. STUDY DESIGN: We evaluated this relationship in the Latina Gestational Diabetes Mellitus Study, a prospective cohort of Hispanic obstetric patients. The Kaiser Physical Activity Survey was used to collect information on physical activity in prepregnancy, early pregnancy and mid-pregnancy. Duration of labor was abstracted from medical records. A total of 725 women with a singleton pregnancy and a spontaneous vaginal delivery were included, which yielded \u3e80% power to detect a clinically meaningful mean difference of 30 minutes. RESULTS: The mean duration of second-stage of labor was 34.3 min (SD 42.02). After adjusting for established risk factors, no significant differences in duration of labor were observed among women according to physical activity level in prepregnancy, early pregnancy, or mid-pregnancy. CONCLUSION: Findings confirm prior literature demonstrating the absence of an association between physical activity and duration of labor