MYNORTHWEST NEWS

Study: Wildfire smoke may increase the risk of pre-term births

Nov 6, 2025, 5:00 AM

wildfire smoke...

Smoke from wildfires obscure the Space Needle and the Seattle skyline on September 12, 2020 in Seattle, Washington. (Photo: Lindsey Wasson, Getty Images)

(Photo: Lindsey Wasson, Getty Images)

With wildfires still burning in Washington, a new study is shedding light on the risk that pollution from those fires poses to pregnant women and their babies.

“We found there was a higher risk of pre-term birth with higher exposure to wildfire smoke,” Dr. Catherine Karr said in an interview provided by UW Medicine.

Karr was one of 42 researchers involved in the nationwide study, which examined 20,000 births from 2006 to 2020.

“Virtually all the women had at least one day with some smoke — some small particles from wildfire smoke,” Karr said.

The timing of when a woman is exposed to smoke during her pregnancy appears to play a role.

Exposure to high concentrations of smoke-days late in a pregnancy showed the strongest association to pre-term births, but so did exposure to lower and moderate levels of smoke-days during the second trimester.

“The second trimester is a period in pregnancy which sees the richest and most intense growth of the placenta,” Karr said in a statement.

Wildfire smoke can interfere with development of placenta

Researchers theorize that the tiny, inhaled smoke particles can enter a woman’s bloodstream and interfere with the development of the placenta.

She said pregnant women need to be aware of the risk and take precautions, particularly in the western half of the U.S., where researchers saw the highest risk.

“Learn about the air quality index or AQI, which is a really handy way of knowing whether the air quality is safe,” Karr said.

She said you can find the AQI on the Environmental Protection Agency’s website and even download an app on your phone.

Researchers suggest local public health departments provide early warnings about smoke events as well as access to clean air, indoor locations.

Read more of Heather Bosch’s stories here.

MyNorthwest News

parenting...

Katrina Guischard

The parenting advice going viral right now: be the pilot, not the passenger

An expert is challenging some of today's most popular parenting trends, and it's striking a chord.

14 hours ago

ritzville i-90 closed visibility...

Jason Sutich

I-90 in Ritzville reopens after dust storm caused multiple collisions

I-90 in Ritzville has reopened after both directions were blocked Friday due to multiple collisions.

24 hours ago

Ballard hit-and-run...

KIRO Newsradio staff

20-year-old sentenced to more than 3 years for deadly 2025 Ballard hit-and-run

The man accused in the hit-and-run death of a pedestrian in Ballard last year has been sentenced to more than three years in prison.

1 day ago

2 box truck fire SODO...

Julia Dallas

Suspects accidentally light themselves on fire while allegedly trying to steal fuel from box trucks in SODO

Two suspects accidentally set themselves on fire while they appeared to be trying to steal fuel from box trucks in the SODO neighborhood.

1 day ago

columbia city school gun...

MyNorthwest Staff

Person in custody after gun seized by staff at high school in Seattle

A person is in custody after a gun was seized by staff at a high school in Seattle.

1 day ago

2 Rick Rizzs...

Manda Factor

Rick Rizzs says goodbye to Mariners booth after 52-year career: ‘I’ve lived my dream’

Rick Rizzs has three games left behind the microphone for the Seattle Mariners, and a lifetime of memories competing for his attention.

1 day ago

Study: Wildfire smoke may increase the risk of pre-term births