On Nov. 4, 2025, a team of scientists led by the University of Washington announced findings published this week in The Lancet journal that show breathing wildfire smoke while pregnant may raise the risk of preterm birth, especially in the western United States.  

Researchers analyzed more than 20,000 births nationwide from 2006 to 2020 and found that exposure to wildfire-related fine-particle pollution during those pregnancies was linked to higher odds of preterm delivery in the West. 

“Wildfires are becoming more frequent and intense, and our findings suggest that smoke exposure during pregnancy may have real consequences for maternal and infant health,” said co-author Dr. Catherine Karr, a UW Medicine pediatrician.  

Karr was one of 42 authors nationwide who studied the smoke exposure statistics. Lead authors included Allison Sherris, a postdoctoral scholar in the Karr lab at the University of Washington’s Department of Environmental and Occupational Health Sciences.  

The researchers emphasize the need for public health guidance tailored to pregnant individuals during wildfire season, including access to clean indoor air, early warnings about smoke events, and strategies to reduce exposure.