Is wildfire smoke safe during pregnancy?

What does the evidence say about wildfire smoke during pregnancy?

1. Across 5,155,026 singleton California births, each 1 microgram per cubic meter rise in average wildfire PM2.5 across pregnancy was associated with slightly higher odds of preterm birth (odds ratio 1.013). 1
2. Of seven wildfire studies examined in one review, six found an association with decreased birth weight, including a Colorado analysis estimating a reduction of 5.7 grams per microgram per cubic meter of exposure. 2
3. Wildfire smoke has been documented to contain toxic carcinogens including benzene and benzo[a]pyrene, though the relative toxicity of wildfire particulate compared with particulate from other sources remains uncertain. 3
4. The exposure-reduction strategies identified for pregnancy are staying indoors with a high-efficiency filter running, using an N95 or P100 respirator when outside, cutting outdoor and strenuous activity, and checking real-time air quality index readings. 2
5. Pregnant people are identified as a vulnerable group alongside young children with asthma, older adults with chronic lung disease and outdoor workers, with running air purifiers and correctly wearing high-quality respiratory protection named as the main protective measures. 3

Is wildfire smoke safe in each trimester?

• First trimester. Smoke season is a good reason to get a filter running at home before you need it. Early pregnancy fatigue already limits what you feel like doing outdoors, so skipping runs and long walks on smoky days costs you little.
• Second trimester. In a California analysis, exposure around week 23 showed one of the clearest links with preterm birth, so mid-pregnancy is not a stretch to ignore. Move workouts indoors when the index climbs.
• Third trimester. Breathlessness is already normal now and smoke makes it worse. Keep one room well filtered, close the windows on bad days, and save a properly fitted N95 for the errands you cannot skip.