RT Journal Article SR Electronic T1 Night work and sick leave during pregnancy: a national register-based within-worker cohort study JF Occupational and Environmental Medicine JO Occup Environ Med FD BMJ Publishing Group Ltd SP 163 OP 168 DO 10.1136/oemed-2018-105331 VO 76 IS 3 A1 Hammer, Paula Edeusa Cristina A1 Garde, Anne Helene A1 Begtrup, Luise Moelenberg A1 Flachs, Esben Meulengracht A1 Hansen, Johnni A1 Hansen, Åse Marie A1 Hougaard, Karin Sørig A1 Kolstad, Henrik A A1 Larsen, Ann Dyreborg A1 Pinborg, Anja Bisgaard A1 Specht, Ina Olmer A1 Bonde, Jens Peter YR 2019 UL http://oem.bmj.com/content/76/3/163.abstract AB Objective The aim of our study was to investigate the acute effect of night work during pregnancy on the risk of calling in sick the following day using register-based information and the workers as their own controls.Methods Using the payroll-based national Danish Working Hour Database, including all public hospital employees in Denmark, we identified 9799 pregnant women with ≥1 day shift and ≥1 night shift and ≥1 day of sick leave during the first 32 pregnancy weeks from January 2007 to December 2013. We performed fixed effects logistic regression, that is, within-worker comparisons, of the risk of sick leave of any duration starting within 24 hours after night shifts of different length versus day shifts.Results Most of the participants were nurses (64%) or physicians (16%). We found an increased relative risk of sick leave following night shifts compared with day shifts during all pregnancy trimesters. The risk was highest for night shifts lasting >12 hours (OR 1.37, 95% CI 1.15 to 1.63 for nurses; OR 1.87, 95% CI 1.69 to 2.08 for physicians) and among women aged >35 years (OR 1.42, 95% CI 1.24 to 1.63).Conclusion Among Danish public hospital employees night shifts during pregnancy, especially shifts longer than 12 hours, increased the risk of calling in sick the following day independent of personal factors and time-invariant confounders in all pregnancy trimesters.