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Bispebjerg Hospital - a part of Copenhagen University Hospital

Night work during pregnancy and maternal health

Research output: Book/ReportPh.D. thesis

  1. Natarbejde og komplikationer i graviditeten

    Research output: Contribution to journalReviewResearchpeer-review

  2. Night work and postpartum depression: a national register-based cohort study

    Research output: Contribution to journalJournal articleResearchpeer-review

  3. Night work and miscarriage: a Danish nationwide register-based cohort study

    Research output: Contribution to journalJournal articleResearchpeer-review

  4. Night work and sick leave during pregnancy: a national register-based within-worker cohort study

    Research output: Contribution to journalJournal articleResearchpeer-review

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Around 10% and 14% of the female workers in Denmark and Europe, respectively, work at night, many of whom are at their childbearing age. Night work during pregnancy may induce sleep disorders along with hormonal changes resulting in several diseases both for the mother and the child. Therefore, the negative health effects of night work during pregnancy may have a major impact on public health and socioeconomic costs. The majority of previous studies in this field have used crude and self-reported information on working hours, and thus could not identify which aspects of night work are primarily related to negative health effects. The overall aim of the PREGNIGHT project was to use nationwide register-based information to: 1) investigate the impact of different dimensions of night work during pregnancy on the risk of hypertension and preeclampsia (HDP), sick leave, and severe postpartum depression (PPD); and 2) identify possible ways of organizing night work during pregnancy that might reduce its potential negative health effects. The dimensions of night work we investigated were: number and duration of night shifts, consecutive night shifts and short intervals between shifts. The source population was identified from the Danish Working Hour Database, which contains nationwide payroll data from all public hospital employees in Denmark. We included all women who gave birth at least once in the period 2007-2015. The study cohort comprised approximately 20,000 women, where most were nurses (64%) or physicians (17%). We found that more than 3 consecutive night shifts during the first 20 pregnancy weeks were associated with 41% increased risk of HDP (study I). If the pregnant woman was obese, all dimensions of night work increased the risk of HDP by 4-5-fold. In study II, we found that night shifts, especially those lasting more than 12 hours, and short shift intervals were associated with a 55% increased risk of sick leave during all pregnancy trimesters independent of personal factors (the participants were their own controls) when compared to day shifts. On the other hand, we found no increased risk of negative health effects among women who worked up to one night shift per week on average during pregnancy, as far as they did not have > 3 consecutive night shifts or were obese. If this result was to be false, the risks are expected to be rather small. In study III we did not find an overall increased risk of PPD in relation to night work. However, women who stopped working night shifts after the 1st trimester had an increased risk suggesting the presence of the healthy worker effect, where women somehow susceptible to PPD are selected out of night work earlier in pregnancy, while women with a relatively better health status continue working night shifts throughout pregnancy. Our findings support the hypothesis that the health effects of night work are more related to the way night shifts are organized rather than the mere presence of night shifts. If pregnant women work night shifts, adequate shift intervals along with reduction of their frequency and duration might reduce sick leave and HDP. Special attention must be paid to women who do not adapt to night work and those with other risk factors for pregnancy complications. All potentially modifiable risk factors for reproductive hazards must be taken into account by health care professionals who advise workers and employers on health risks of night work during pregnancy.
Original languageEnglish
Number of pages120
Publication statusPublished - 11 Apr 2019

ID: 57551225