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Some jobs may come with more than just a paycheck.
A new study suggests that a mother’s line of work before, during and after pregnancy could influence her baby’s brain development.
In certain careers, researchers found, she may even be more likely to have a child with autism, a developmental disorder that affects how people communicate, behave and interact with others.
Diagnoses in the US have climbed sharply in recent years, from 1 in 150 children in 2000 to 1 in 31 by 2022. Adults ages 26 to 34 have also seen a 450% increase in diagnoses between 2011 and 2022.
Scientists still aren’t sure what causes autism, though research suggests a combination of genetic and environmental factors likely play a role.
Now, a team at the Johns Hopkins Bloomberg School of Public Health say mothers in high-stress jobs or roles involving toxic chemical exposure could see higher autism rates in their children.
Researchers analyzed data from Denmark covering 1,702 children diagnosed with autism and born between 1973 and 2012. Those cases were compared with more than 108,000 children without the condition, matched by sex and birth year.
About 70% of both groups were boys, and nearly half were born in the 1990s.
The team also examined mothers’ employment histories before conception, during pregnancy and through early infancy, using records from Denmark’s national pension registry.
After adjusting for factors that could skew the results — including maternal age, smoking during pregnancy, socioeconomic status and history of psychiatric conditions — patterns began to emerge.
The team found that children whose mothers worked in the military or other defense roles up to one year before or during pregnancy were 59% more likely to be diagnosed with autism.
Researchers recorded a 24% higher prevalence of autism among children whose mothers worked in ground transportation, while the figure reached 59% in the judicial sector.
The possible associations were seen across jobs held in the year before conception, during pregnancy and through infancy, though they weakened during the early months after birth.
Not every occupation showed a connection. No clear link was found for mothers working in agriculture, despite potential pesticide exposure.
And several other fields — including air transportation, chemical processing and cleaning services — did not show significant results once other factors were taken into account.
The researchers believe the differences may come down to workplace exposures. In defense jobs, that could include lead from handling artillery, along with exhaust fumes and industrial solvents.
In transportation roles, exposure to exhaust and fine particulate matter may play a role, they suggested.
The team also pointed to stress as a possible factor, particularly in high-pressure jobs such as the judicial sector, which may contribute to fatigue and inflammation during pregnancy and influence brain development.
Looking ahead, the researchers are calling for studies to examine specific toxic exposures in these occupations and how they can affect early development.
But not everyone is swayed by the findings.
Critics point out that the large number of statistical tests run across several job categories and subgroups increases the likelihood that some results occur by chance, particularly in groups with very small sample sizes.
For example, the finding that mothers working in the judicial sector were 59% more likely to have a child diagnosed with autism is based on just 29 cases.
Outside experts also say important factors — including fathers’ occupations, detailed job roles and changes in autism diagnosis criteria over time — were not fully accounted for, which could distort the results.
“For women who would like to become a mum: please choose a job you enjoy,” Rosa Hoekstra, a professor of developmental disabilities at King’s College London, who was not involved in the study, said in a statement.
“Don’t let this study put you off a career in public administration or in the judicial sector.”
