Pregnant women who work nights may have a greater risk of miscarriage

pregnant woman
Credit: CC0 Public Domain

Working two or more night shifts in a week may increase a pregnant woman's risk of miscarriage the following week by around a third, shows a prospective study published online in Occupational & Environmental Medicine.

Previous studies have suggested that face a greater risk of miscarriage if they work , but they have been based on self-reported shift work and have not quantified the level of increased risk or the amount of involved.

For this study the authors accessed payroll data on 22,744 pregnant working in public services, mainly hospitals, in Denmark, and linked that with data from Danish national registers on births and admissions to hospital for miscarriage to determine how the risk of miscarriage between weeks 4-22 of was influenced by night work.

Overall 377,896 pregnancy weeks were included—an average of 19.7 weeks per woman.

After week eight of pregnancy, women who had worked two or more night shifts the previous week had a 32% higher risk of miscarriage compared with women who had not worked any night shifts that week.

And the risk of miscarriage increased with the number of night shifts worked per week and also by numbers of consecutive night shifts.

The association between night work and the risk of was stronger after pregnancy week 8. "This may be explained by the decline in the proportion of chromosomally abnormal fetuses with gestational age, which makes an association with environmental exposure more easily detectable among later miscarriages," the authors say.

This is an observational study, and as such, can't establish cause, and the authors point out that data on miscarriages, particularly early miscarriages, were incomplete.

But, as around 14% of women in Europe report working at night at least once a month, the findings have relevance for working pregnant women as well as their employers, physicians and midwives, they emphasise. "Moreover, the results could have implications for national occupational health regulations."

In terms of the underlying mechanism responsible for the association, women working night shifts are exposed to light at night which disrupts their circadian rhythm and decreases the release of melatonin. Melatonin has been shown to be important in maintaining a successful pregnancy, possibly by preserving the function of the placenta.

More information: Night work and miscarriage: a Danish nationwide register-based cohort study, Occupational & Environmental Medicine DOI: 10.1136/oemed-2018-105592

Citation: Pregnant women who work nights may have a greater risk of miscarriage (2019, March 25) retrieved 11 December 2023 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Explore further

Risk of miscarriage linked strongly to mother's age and pregnancy history


Feedback to editors