Although nurses are frequently exposed to physical demands and chemicals at work during pregnancy, results from studies of these effects on fetal growth are inconclusive. We investigated the relationship between certain occupational exposures and term low birthweight (LBW) among participants in the Nurses' Health Study II. In 2001, data were obtained from a self-administered questionnaire on occupational and lifestyle factors during the most recent pregnancy. A total of 6,159 term births were analyzed. Logistic regression was used to model the risk associated with term LBW and work schedule, standing, lifting, and exposure to chemicals and x-ray radiation. Of the 6,159 term births, 58 (0.9%) were LBW (weighed less than 5.5 pounds). For every hour of standing, the risk of delivering a LBWinfant at term was increased by 15% [95% confidence interval (95% CI): 1.02 - 1.29], after adjusting for age, parity, and other occupational factors. Number of hours worked per week [odds ratio (OR) ¼ 1.02, 95% CI: 0.99, 1.04] and heavy lifting (number of times the subject lifted 25 pounds or more per day) (OR ¼ 0.96, 95% CI: 0.91, 1.02) showed no relation to term LBW. These data from a large cohort study of U.S. nurses suggest that prolonged standing at work may increase the risk of having a LBWinfant. Measures to limit standing during pregnancy may decrease the incidence of term LBW in infants of women working in this profession.
American Journal of Epidemiology; 41st Annual Meeting Society for Epidemiologic Research Chicago, Illinois, June 24-27, 2008