August 10, 2026
Air Quality & Health | August 7, 2026 | 2 min read
A new national study finds that wildfire smoke has overtaken cars and industry as the leading source of unhealthy fine-particle pollution experienced during pregnancy in the US. Here's what the research found.
Researchers at the University of Maryland, publishing in Frontiers in Environmental Health, analyzed roughly 64.5 million pregnancies across 2,842 counties in 48 states between 2003 and 2019. Using computer models, they estimated how much of each pregnant person's exposure to fine particle pollution, or PM2.5, came specifically from wildfire smoke versus other sources like vehicles and industry.
Overall PM2.5 exposure during pregnancy dropped substantially over the study period, reflecting broad air quality gains. But wildfire smoke's share of that pollution more than doubled, rising from about 3.7% in 2003 to 8.2% by 2019 nationally. In the Northwest specifically, wildfires' contribution surged from roughly 5.1% to 13.3%. By the end of the study period, wildfire smoke accounted for about 65% of the days when PM2.5 exceeded the EPA's unhealthy threshold during pregnancy.
The study's lead author, Menglu Liang of the University of Maryland, said wildfire pollution burdens were highest for low-income, rural, American Indian, and Alaska Native communities, along with areas that have limited maternity care resources.
Not on its own. As several outlets covering the study have noted, this was an exposure study, not an outcomes study — researchers measured how much smoke pregnant people were exposed to, not birth weight, gestational age, or other outcomes directly. The authors point to separate prior research linking PM2.5 exposure during pregnancy to risks like preterm birth and low birth weight, and note that smoke-derived particles may carry added risk compared to equivalent pollution from other sources. The study also didn't account for protective steps some people may have taken, like using air filtration or relocating temporarily during smoke events. For anyone with questions about air quality and pregnancy, a doctor or maternity care provider is the right resource for personal guidance.
The study period ends in 2019 and doesn't include some of the most severe wildfire seasons since, including 2020 and 2023's widespread Canadian smoke events — meaning the true current picture may be even more pronounced.
Prep your home for wildfire smoke season
Smoke particles get inside even with doors and windows shut. A few steps to take now:
Sources: Frontiers in Environmental Health, Air Quality News, Inside Climate News, Medical Daily, Stateline.
