Study links late-pregnancy wildfire smoke exposure to higher autism diagnosis risk in children

By Tahani Elghazaly
Published January 24, 2026

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A U.S. study has highlighted an unexpected environmental factor that may be associated with a higher likelihood of autism diagnoses in children: maternal exposure to wildfire smoke during the third trimester.

The study, led by Tulane University researchers and published in Environmental Science & Technology, analyzed more than 200,000 births in Southern California from 2006 to 2014, including 3,356 children diagnosed with autism by age five.

Reports of the findings indicate a dose-related association: exposure to 1–5 smoke days in late pregnancy was linked to about an 11% higher likelihood of an autism diagnosis, 6–10 smoke days to about 12%, and more than 10 smoke days to 23%, compared with no wildfire-smoke exposure during pregnancy.

Researchers stressed the study does not prove causation, but adds to growing evidence that air pollution during pregnancy may affect fetal neurodevelopment.

Public health guidance (Canada and the U.S.)

Given intensifying wildfire seasons across North America, official guidance recommends reducing smoke exposure when possible and keeping indoor air as clean as possible. The U.S. CDC notes that if a pregnant person must go outside during heavy smoke, a well-fitting N95 respirator is recommended. Health Canada provides preparedness steps aimed at maintaining cleaner indoor air during smoke events