Key national findings include:Overall decline: Average daily prenatal PM2.5 exposure from all sources decreased by approximately 34% over the study period, reflecting broad air quality improvements. The wildfire offset: When wildfire emissions were excluded from the models, the decrease was steeper (37%), indicating that wildfire smoke actively undermined hard-won regulatory gains. Doubled proportional share: Wildfires’ contribution to total prenatal PM2.5 exposure increased from 3.7% in 2003 to 8.2% in 2019. Dominance on high-pollution days: By 2019, wildfire smoke accounted for roughly 65% of all prenatal “exceedance days”—days when PM2.5 levels surpassed the EPA unhealthy threshold of 35 micrograms per cubic meter. The authors emphasise that public health interventions, air filtration resources, and protective measures must be strategically targeted to vulnerable populations and underserved geographic regions.