You have probably watched a hazy orange sky move in during fire season, or caught the smell of smoke miles from the flames.
Most of us think of it as a lung problem, maybe a scratchy throat or a cough. For pregnant women, the trouble may run deeper than that.
A large US study tracking nearly 900,000 pregnancies has linked wildfire-related air pollution during pregnancy to a roughly 30 percent higher risk that the child will later be diagnosed with autism.
The findings were published October 26, 2026 in JAMA Pediatrics by researchers at Rutgers School of Public Health, who followed children enrolled in Medicaid across the United States.
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What the researchers actually measured
The team looked at 893,212 mother-child pairs, with children born between 2007 and 2014.
They matched each pregnancy with weekly estimates of wildfire-related fine particles in the air at the mother's address.
For every small jump in wildfire-related fine particles during pregnancy, the risk of a later autism diagnosis in the child rose by about 30 percent.
The link held after the team accounted for other sources of air pollution, like traffic and industry.
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Among pregnancies with the lowest levels of other air pollution, those in the top 10 percent for wildfire smoke exposure had about 50 percent higher odds of an autism diagnosis.
The pattern looked different for ADHD. Prenatal wildfire exposure showed no clear link to a later ADHD diagnosis in the same group of children.
The second half of pregnancy appeared most vulnerable
The risk did not look the same across all of pregnancy. The association with autism was strongest when the smoke exposure happened after about week 15, during the second and third trimesters.
That timing fits the brain's own clock. Pregnancy is a stretch of rapid brain development, and the researchers wrote that outside exposures during that window may interfere with how it unfolds.
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Lead author Stefania Papatheodorou is an epidemiologist at Rutgers School of Public Health.
In a statement from the Harvard T.H. Chan School of Public Health, she said smoke exposure can happen even when the sky looks clear.
"Wildfire smoke can travel far beyond the communities where fires are burning, and exposure may occur even when smoke is not visible," she said.
How to protect yourself when the air turns smoky
The Environmental Protection Agency lists pregnant women among the sensitive groups who should be careful when the Air Quality Index climbs above 100. During a smoke event, that usually means staying indoors.
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Keep windows and doors closed. Set the air conditioner to recirculate. A portable air cleaner with a HEPA filter can help in the room where you spend the most time.
If you have to go outside while the air is thick, a well-fitting N95 or KN95 respirator filters out fine particles that cloth and surgical masks let through.
Check AirNow.gov or your local air quality readings before heading out.
The study was observational, so it cannot prove that wildfire smoke causes autism.
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The researchers also noted that the findings come from Medicaid-enrolled families, who may differ from the wider US population.
AirNow posts an updated AQI by ZIP code every hour and sends free email alerts when smoke moves into your area.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.