Night Shifts During Pregnancy Linked to Child Risks, Study Finds
Research published online in Occupational & Environmental Medicine and featured on News-Medical indicates that night shifts during pregnancy are associated with an elevated likelihood of screening-detected neurodevelopmental abnormalities in children by four years of age. At the same time, nightly prenatal sleep length during this period may modify this observed association, exploratory findings suggest.
Night shift work during pregnancy has been linked by investigators to adverse health consequences for both mothers and babies, including neurodevelopmental problems that may stem from circadian rhythm and sleep disruptions. Scientists drew on nationwide survey data for around 100,000 pregnant women from the Japan Environment and Children’s Study, who were enrolled between January 2011 and March 2014.
Key Clinical Takeaways:
- Children of mothers who continued night shifts throughout pregnancy faced higher risks of developmental screening abnormalities in communication, fine motor skills, and personal-social functioning.
- A separate exploratory analysis revealed that prenatal sleep duration of 10 hours or more was associated with an 80% heightened risk of abnormalities across domains.
- Researchers suggest that maternal inflammation from persistent night work may preferentially affect neural pathways tied to fine motor function.
Survey Data and Screening Methods From the Japan Environment and Children’s Study
To determine whether potentially modifiable prenatal factors—such as adjustments to sleep duration and night shift schedules—exist, investigators analyzed the connections between maternal night shift employment and child neurodevelopment. The women were surveyed in the first and second or third trimesters and answered questions about the number of night shifts they worked in a month.
Their responses were divided into three groups: no night shifts reported in either survey, covering 27,655 women; night shifts in the first survey but not the second, termed discontinued night shifts, involving 1,779 women; and night shifts in both surveys, termed continued night shifts, accounting for 2,084 women. Prenatal sleep length was calculated from self-reported bedtime and wake-up times in the second or third trimester. Sleep length was categorised as short if less than 6 hours, moderate if 6 to 9 hours, and long if 10 or more hours.
Child neurodevelopmental abnormalities at the age of four were assessed using a developmental screening tool, specifically the Japanese version of the Ages and Stages Questionnaire, Third Edition, known as J-ASQ-3. This tool is made up of five domains: communication, gross motor skills, fine motor skills covering the ability to make small, precise, deliberate movements, problem solving, and personal-social functioning, which includes interpersonal skills, emotional or behavioural development, and awareness of personal boundary and space.
The evaluation ultimately incorporated 31,528 mothers who were employed during their first trimester and completed the developmental questionnaire when their offspring reached four years of age. Out of all the four-year-olds evaluated, 4,189 children—representing just over 13%—met the criteria for high risk regarding abnormalities in at least one of the five J-ASQ-3 domains. This included 1,210 children for communication, 1,599 for gross motor skills, 1,906 for fine motor skills, 913 for problem solving, and 1,495 for personal-social functioning.
Observed Neurodevelopmental Risks Across Specific Domains
Relative to offspring of women who performed no night work, youngsters whose mothers stopped working night shifts exhibited a greater likelihood of developmental screening abnormalities exclusively in the fine motor skills category, demonstrating a 24% elevated risk. Conversely, when mothers reported working night shifts across both surveys, elevated risks emerged in three separate categories: a 29% increase for communication abilities, a 34% rise for fine motor proficiency, and a 31% escalation in personal-social capabilities.
A statistically significant connection was found exclusively within the fine motor skills category, regardless of whether night shifts were maintained or abandoned. Investigators propose that persistent night employment could trigger maternal inflammation, which might selectively impact the neural pathways responsible for fine motor coordination.
A separate exploratory analysis showed that the observed association between night shift patterns and the child’s neurodevelopmental risk differed according to how long the mothers slept. Sleeping for 10 hours or longer during pregnancy was linked to an 80% greater chance of abnormalities across any of the five domains when measured against a prenatal sleep duration of six to nine hours. Rather than serving as a harmful exposure by itself, the study authors note that sleeping for extended periods prior to birth might additionally indicate underlying fatigue, anaemia, inflammation, or subclinical depression.
Study Limitations Suggest Flexible Schedules for Pregnant Night Workers
This is an observational study, and as such, cannot establish cause and effect. The study authors note that they were unable to control for individual chronotype, work duties, shift rotation schedules, light exposure, or the exact timing of when night shifts were stopped, any of which could have impacted the results.
Given these findings, the authors of the study suggest that employers might want to contemplate offering flexible work arrangements for pregnant employees working night shifts.
Disclaimer: The information provided in this article is for educational and scientific communication purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider regarding any medical condition, diagnosis, or treatment plan.