Physical activity, physical exertion, and miscarriage risk in women textile workers in Shanghai, China

Background Strenuous occupational physical activity and physical demands may be risk factors for adverse reproductive outcomes. Methods A retrospective study in the Shanghai, China textile industry study collected women's self-reported reproductive history. Occupational physical activity assessment linked complete work history data to an industry-specific job-exposure matrix. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by multivariate logistic regression for the first pregnancy outcome and utilized generalized estimating equations to consider all pregnancies per woman. Results Compared with women employed in sedentary jobs, a reduced risk of miscarriage was found for women working in jobs with either light (OR 0.18, 95% Cl: 0.07, 0.50) or medium (OR 0.24, 95% CI: 0.08, 0.66) physical activity during the first pregnancy and over all pregnancies (light OR 0.32, 95% CI: 0.17, 0.61; medium OR 0.43, 95% Cl: 0.23, 0.80). Frequent crouching was associated with elevated risk (OR 1.82, 95% CI: 1.14, 2.93: all pregnancies per woman). Conclusions Light/medium occupational physical activity may have reduced miscarriage risk, while specific occupational characteristics such as crouching may have increased risk in this cohort. Am. J. Ind. Med. 53:497-505, 2010. (C) 2010 Wiley-Liss. Inc.