Backgroud
An increasing number of original studies suggest that exposure to shift work and long
working hours during pregnancy could be associated with the risk of adverse pregnancy
outcomes, but the results remain conflicting and inconclusive.
Objective
To examine the influences of shift work and longer working hours during pregnancy
on maternal and fetal health outcomes.
Data Sources
Five electronic databases and 3 gray literature sources were searched up to March
15, 2019.
Methods of Study Selection
Studies of all designs (except case studies and reviews) were included, which contained
information on the relevant population (women who engaged in paid work during pregnancy);
exposure (rotating shift work [shifts change according to a set schedule], fixed night
shift [typical working period is between 11:00 pm and 11:00 am] or longer working
hours [>40 hours per week]);comparator (fixed day shift [typical working period is
between 8:00 am and 6:00 pm] or standard working hours [≤40 hours per week]); and
outcomes (preterm delivery, low birthweight [birthweight <2500 g], small for gestational
age, miscarriage, gestational hypertension, preeclampsia, intrauterine growth restriction,
stillbirth, and gestational diabetes mellitus).
Tabulation, Integration, and Results
From 3305 unique citations, 62 observational studies (196,989 women) were included.
“Low” to “very low” certainty evidence from these studies revealed that working rotating
shifts was associated with an increased odds of preterm delivery (odds ratio, 1.13;
95% confidence interval, 1.00–1.28, I2 = 31%), an infant small for gestational age (odds ratio, 1.18, 95% confidence interval,
1.01–1.38, I2 = 0%), preeclampsia (odds ratio, 1.75, 95% confidence interval, 1.01–3.01, I2 = 75%), and gestational hypertension (odds ratio, 1.19, 95% confidence interval,
1.10–1.29, I2 = 0%), compared to those who worked a fixed day shift. Working fixed night shifts
was associated with an increased odds of preterm delivery (odds ratio, 1.21; 95% confidence
interval, 1.03–1.42; I2 = 36%) and miscarriage (odds ratio, 1.23; 95% confidence interval, 1.03–1.47; I2 = 37%). Compared with standard hours, working longer hours was associated with an
increased odds of miscarriage (odds ratio, 1.38; 95% confidence interval, 1.08–1.77;
I2 = 73%), preterm delivery (odds ratio, 1.21; 95% confidence interval, 1.11–1.33; I2 = 30%), an infant of low birthweight (odds ratio, 1.43; 95% confidence interval,
1.11–1.84; I2 = 0%), or an infant small for gestational age (odds ratio, 1.16, 95% confidence interval,
1.00–1.36, I2 = 57%). Dose–response analysis showed that women working more than 55.5 hours (vs
40 hours) per week had a 10% increase in the odds of having a preterm delivery.
Conclusion
Pregnant women who work rotating shifts, fixed night shifts, or longer hours have
an increased risk of adverse pregnancy outcomes.
Key words
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Article info
Publication history
Published online: July 02, 2019
Accepted:
June 27,
2019
Received in revised form:
June 21,
2019
Received:
May 1,
2019
Footnotes
The authors report no conflict of interest.
This project is funded by a Government of Alberta Occupational Health and Safety (OHS) Futures Research Grant. The OHS was not involved with the preparation and submission of the manuscript. MHD is funded by a Heart & Stroke Foundation of Canada (HSFC)/Health Canada Improving Heart Health for Women Award, National and Alberta HSFC New Investigator Award. This work was also supported by the Alberta Strategy for Patient-Oriented Research (SPOR) SUPPORT Unit Knowledge Translation Platform, which is funded by Alberta Innovates and the Canadian Institutes of Health Research (CIHR). KN is funded by a HSFC Alberta New Investigator Award and the HSFC/CIHR Women’s Heart and Brain Health Mid-Career Research Chair.
PROSPERO registration number: CRD42018094400.
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