Night Shifts in Pregnancy Linked to Child Screening Flags
A Japanese study of more than 31,000 mothers found higher risks of developmental abnormalities at age four. The authors stress that it cannot prove cause and effect.
Women who work night shifts during pregnancy are more likely to have children flagged by developmental screening at age four, according to research published online in Occupational & Environmental Medicine.
The team drew on the Japan Environment and Children's Study, a nationwide survey of around 100,000 pregnant women enrolled between January 2011 and March 2014. Women reported how many night shifts they worked each month, in the first trimester and again in the second or third. The analysis covered 31,528 mothers who worked in the first trimester and who completed the child development questionnaire when their children were four.
Three groups were compared. In 27,655 cases there were no night shifts. In 1,779 the mother stopped night work after the first survey. In 2,084 she kept working nights.
What the screening found
Children were assessed with the Japanese version of the Ages and Stages Questionnaire, Third Edition, which covers communication, gross motor skills, fine motor skills, problem solving and personal-social functioning. In all, 4,189 children, just over 13%, were classed as high risk in at least one domain.
By domain, 1,210 children (4%) were flagged for communication, 1,599 (5%) for gross motor skills, 1,906 (6%) for fine motor skills, 913 (3%) for problem solving and 1,495 (5%) for personal-social functioning.
Children whose mothers stopped night work had a 24% higher risk, but only for fine motor skills. For children whose mothers kept working nights, risks were higher in three areas: communication by 29%, fine motor skills by 34% and personal-social functioning by 31%.
Only fine motor skills showed a significant association whether night shifts were continued or stopped. The researchers suggest that maternal inflammation linked to persistent night work may affect neural pathways involved in fine motor function.
Sleep length and limits
An exploratory analysis found the link differed with how long mothers slept. Prenatal sleep of ten hours or more was associated with an 80% higher risk of abnormalities in any domain, compared with six to nine hours. The authors say long sleep may reflect fatigue, subclinical depression, inflammation or anaemia rather than being harmful in itself.
The study is observational, so it cannot establish cause and effect. The researchers could not account for shift rotation, individual chronotype, workload, light exposure or when women stopped night work. Based on the findings, they say employers may want to consider flexible schedules for pregnant night shift workers.
Source: News-Medical