First-trimester occupational exposures and hypertensive disorders of pregnancy among US nurses

Background Limited and conflicting data exist regarding the impact of first-trimester nursing occupational exposures on hypertensive disorders of pregnancy (HDP). Aims To investigate whether first-trimester night shift work, work hours and work-related activities are associated with HDP. Methods We conducted a cross-sectional analysis of 6610 women within the Nurses' Health Study II. We used multiple logistic regression to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) for the relation of occupational exposures to HDP. Results Nine per cent of respondents reported an HDP in the index pregnancy (gestational hypertension: n = 354, 5%, preeclampsia: n = 222, 3%). First-trimester fixed or rotating night shift work was not significantly associated with gestational hypertension or preeclampsia compared to day shift work only. Compared to those working 21-40 h/week, working overtime (& GE;41 h/week) was not associated with gestational hypertension but was associated with 43% higher odds of preeclampsia (95% CI 1.02, 2.00). For part-time work (& LE;20 h/week), the OR was 0.76 (95% CI 0.56, 1.02) for gestational hypertension and 0.64 (95% CI 0.43, 0.97) for preeclampsia. The odds of preeclampsia were 3% higher per additional hour worked per week (95% CI 1.01-1.04). Compared to 0-4 h spent standing or walking per day, standing or walking & GE;9 h daily was associated with 32% lower odds of gestational hypertension (95% CI 0.47, 0.99) but was not significantly associated with preeclampsia. Frequency of heavy lifting was not associated with either hypertensive disorder or pregnancy. Conclusions Among nurses, working overtime was associated with higher odds of preeclampsia. Nurses work in a unique occupational environment that can require night shift work, long working hours, prolonged standing and heavy lifting. In this study of US nurses (n = 6610), we observed an association between higher first-trimester working hours and higher odds of both preeclampsia and gestational hypertension. Our findings suggest that consideration of optional work-hour limitations during pregnancy could be beneficial.