Working night shifts during pregnancy may increase the risk for miscarriage in women who work as frequently as 2 nights per week, according to study results published in Occupational & Environmental Medicine.

A cohort of 22,744 pregnant women were identified from the Danish Working Hour Database. Risk for miscarriage from week 4 to 22 of gestation was calculated via Cox regression.

Compared with women who did not work night shifts, women who worked 2 or more night shifts the previous week had an increased risk for miscarriage after week 8 of gestation (hazard ratio (HR), 1.32). Risk for miscarriage at 3 to 21 weeks of gestation was increased in dose-dependent patterns according to accumulated number of night shifts.

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“Although our population was based on a nationwide cohort, it primarily consisted of women working in public hospitals, who may have more health-promoting behavior compared with the general Danish population,” the authors noted.

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“The new knowledge has relevance for working pregnant women as well as their employers, physicians and midwives. Moreover, the results could have implications for national occupational health regulations,” concluded the investigators.


Begtrup LM, Specht IO, Hammer PEC, et al. Night work and miscarriage: a Danish nationwide register-based cohort study [published online March 25, 2019]. Occup Environ Med. doi:10.1136/oemed-2018-105592