As wildfire seasons grow longer and more intense across the United States, a major new study reveals important findings about how smoke exposure affects pregnant women and their babies.
The growing threat
Wildfires are becoming more frequent and severe due to climate change, exposing millions of Americans to smoke-filled air. For pregnant people, this isn’t just an inconvenience—it’s a potential health risk.
What the research found
Scientists studied over 20,000 pregnancies across all 48 continental states between 2006 and 2020, tracking day-by-day exposure to wildfire smoke throughout each pregnancy. Here’s what they discovered:
In Western states, where wildfire smoke is most intense, pregnant women are exposed to:
- Moderate to high smoke levels (5-10+ micrograms per cubic meter)
- Multiple consecutive days with wildfire smoke in the air (“smoke waves”)
- Had increased odds of preterm birth (delivering their babies before 37 weeks)
The risk was highest when smoke levels were intense and lasted for several days in a row—not just isolated smoky days.
Timing matters
Interestingly, the study found that when during pregnancy someone is exposed to smoke may be as important as how much:
- Mid-pregnancy (around weeks 14-27): More sensitive to lower-intensity, persistent smoke
- Late pregnancy (weeks 28+): More vulnerable to high-intensity smoke events
Understanding the numbers
About 1 in 10 babies in the U.S. is born preterm. Premature birth can lead to serious health challenges including breathing problems, developmental delays, and other complications. While wildfire smoke isn’t the only cause, this research shows it’s a contributing factor we can potentially address.
What this means for you
If you’re pregnant or planning to become pregnant:
During wildfire season:
- Monitor air quality through apps like AirNow or local weather services
- Stay indoors with windows closed when smoke is present
- Use air purifiers with HEPA filters if possible
- Avoid outdoor exercise on smoky days
- Consider wearing N95 or KN95 masks if you must go outside
The bigger picture: This research highlights why pregnant people should be prioritized in public health advisories during wildfire events. Communities, especially in Western states, need better resources to help expecting families protect themselves during prolonged smoke episodes.
Looking ahead
As climate change continues to fuel more intense wildfire seasons, protecting pregnant people from smoke exposure becomes increasingly important. This study provides critical evidence that can inform:
- Targeted public health warnings during wildfire events
- Better guidance for healthcare providers
- Community-level interventions like clean air shelters
- Policies to help vulnerable populations during smoke emergencies
The bottom line: If you’re pregnant and live in an area affected by wildfires, taking steps to reduce smoke exposure—especially during multi-day smoke events—is an important way to protect both your health and your baby’s development.
Title: Wildfire-specific fine particulate matter and preterm birth: a US ECHO Cohort analysis
Authors: Allison R Sherris, PhD; Logan C Dearborn, MPH; Dana E Goin, PhD; Christine T Loftus, PhD; Adam A Szpiro, Prof; Joan A Casey, PhD; Sindana D Ilango, PhD; Jyoti Angal, PhD; Deborah H Bennett, Prof; Miatta A Buxton, PhD; Carlos A Camargo, Prof; Kecia N Carroll, Prof; Marissa L Childs, PhD; Camille Cioffi, PhD; Lisa A Croen, PhD; Dana Dabelea, Prof; Stephanie M Eick, PhD; Shohreh F Farzan, PhD; Assiamira Ferrara, MD PhD; Erika Garcia, PhD; Alison Gemmill, PhD; Frank Gilliland, MD PhD; Rima Habre, ScD; Irva Hertz-Picciotto, Prof; Alison E Hipwell, Prof; Deborah Hirtz, Prof; Margaret R Karagas, Prof; Daphne Koinis-Mitchell, Prof; Amii M Kress, PhD; Leslie D Leve, Prof; Donghai Liang, PhD; Kristen Lyall, ScD; Lacey A McCormack, PhD; Cindy T McEvoy, Prof; Hooman Mirzakhani, MD PhD; Rachel Morello-Frosch, Prof; Zhongzheng Niu, PhD; Thomas G O’Connor, Prof; Alicia K Peterson, PhD; Rebecca J Schmidt, Prof; Catherine J Karr, Prof; Amy M Padula, PhD
