Working night shifts during pregnancy is linked to a heightened risk of neurodevelopmental abnormalities detected by screening in the child by the age of 4, News-Medical reported, citing new research published online in Occupational & Environmental Medicine.
Night shift work during pregnancy has long been associated with unfavorable health outcomes for both mother and child, including neurodevelopmental issues potentially related to body clock and sleep disturbances, according to the researchers. To explore these associations further and identify modifiable prenatal factors, investigators drew on nationwide survey data for approximately 100,000 pregnant women from the Japan Environment and Children’s Study (JECS) enrolled between January 2011 and March 2014, as detailed by News-Medical.
Survey Categories and Screening Methods in the Japan Environment and Children’s Study
The participating women answered questions about their monthly night shift counts during surveys conducted in their first and second or third trimesters. Their responses were divided into three specific groups: 27,655 women reported no night shifts in either survey; 1,779 women reported night shifts in the first survey but not the second, classified as discontinued night shifts; and 2,084 women reported night shifts in both surveys, classified as continued night shifts, News-Medical reported.
Prenatal sleep length was calculated from self-reported bedtimes and wake-up times during the second and third trimesters. Researchers categorized sleep duration as short if it was less than 6 hours, moderate if it spanned 6 to 9 hours, and long if it reached 10 or more hours. Child neurodevelopmental abnormalities at age 4 were assessed using the Japanese version of the Ages and Stages Questionnaire, Third Edition (J-ASQ-3). This developmental screening tool comprises five domains: communication, gross motor skills, fine motor skills, problem-solving, and personal-social functioning, as outlined by News-Medical.
Developmental Screening Results at Age Four
A total of 31,528 mothers who worked in the first trimester and completed the child development questionnaire when their children reached age 4 were included in the final analysis. Among them, 4,189 children—just over 13% of the total cohort—were classified as high risk for an abnormality in at least one of the five J-ASQ-3 domains, according to News-Medical. Specifically, 1,210 children or 4% scored as high risk for communication, 1,599 or 5% for gross motor skills, 1,906 or 6% for fine motor skills, 913 or 3% for problem-solving, and 1,495 or 5% for personal-social functioning.
Compared with children of mothers who did not work night shifts, children of mothers who discontinued night shift work showed a 24% higher risk of developmental screening abnormalities, but only within the fine motor skills domain. Meanwhile, children whose mothers continued night shifts throughout their pregnancy faced elevated risks across three separate domains compared to the non-night-shift group. These included a 29% higher risk in communication skills, a 34% higher risk in fine motor skills, and a 31% higher risk in personal-social functioning, News-Medical reported. Notably, only the fine motor skills domain showed a significant association regardless of whether night shifts were continued or discontinued. One possible explanation is that maternal inflammation associated with persistent night work may preferentially affect neural pathways involved in fine motor function,
the researchers suggested.
Long prenatal sleep duration correlates with higher neurodevelopmental risk
A separate exploratory analysis revealed that the observed association between night shift patterns and child neurodevelopmental risk varied depending on how long mothers slept. Prenatal sleep durations of 10 or more hours were associated with an 80% higher risk of abnormalities in any of the five domains when compared against prenatal sleep lengths of 6 to 9 hours, according to News-Medical. The researchers noted that long prenatal sleep duration might reflect underlying fatigue, subclinical depression, inflammation, or anemia rather than acting as a harmful exposure by itself.
Because the investigation was observational, it cannot establish a direct cause-and-effect relationship. The researchers also acknowledged that they could not account for shift rotation systems, individual chronotypes, workload, light exposure, or the precise timing of night shift discontinuation, all of which could influence the findings. In light of these results, the study authors suggested that employers might want to consider flexible work schedules for pregnant night shift workers.
Frequently Asked Questions About Pregnancy Night Shifts and Child Development
What specific screening tool was used to evaluate the children at age 4?
Researchers used the Japanese version of the Ages and Stages Questionnaire, Third Edition (J-ASQ-3), which evaluates communication, gross motor skills, fine motor skills, problem-solving, and personal-social functioning.
How many mothers were included in the final analysis of the Japan Environment and Children’s Study?
The final analysis included 31,528 mothers who worked in the first trimester and completed the child development questionnaire when their children turned 4 years old.
What percentage of the children were classified as high risk for developmental abnormalities?
Just over 13%, or 4,189 of the 4-year-olds evaluated, were classified as high risk in at least one of the five J-ASQ-3 screening domains.
Did sleep duration alter the association between night shifts and neurodevelopmental risks?
Exploratory findings showed that prenatal sleep durations of 10 or more hours were linked to an 80% higher risk of abnormalities across the five domains compared to sleep lengths of 6 to 9 hours.
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