Is going outside on a bad air quality day safe during pregnancy?

What does the evidence say about going outside on a bad air quality day during pregnancy?

1. Everyday air pollutants including PM2.5, PM10, ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide are all linked to a higher chance of adverse pregnancy outcomes, and the standing advice is to check daily air quality reports and schedule outdoor activity for when pollution runs lower. 1
2. A pooled analysis found that PM10 levels above 10 micrograms per cubic meter across pregnancy were associated with a 49% higher chance of preterm birth, while ozone exposure at typical urban levels raised the odds by about 5%. 2
3. The same pooled analysis found PM2.5 levels above 10 micrograms per cubic meter across pregnancy were associated with a 28% higher chance of low birth weight, compared with a 13% increase at lower PM2.5 levels. 2
4. Air pollution is a specific pregnancy concern because ciliary clearance in the airways slows and mucus becomes more abundant, and official travel guidance for pregnant people recommends monitoring air quality reports and following the advisories meant for sensitive groups on higher-pollution days. 3
5. A systematic review of N95 respirator use in pregnancy found no significant difference in maternal heart rate, respiratory rate, oxygen saturation, or fetal heart rate compared with short-duration use in non-pregnant people, though data on wearing one for many hours at a stretch is still limited. 4

Is going outside on a bad air quality day safe in each trimester?

• First trimester. Fatigue and nausea already limit outdoor plans early on, so skipping a run or long walk on a high-pollution day costs little. This is also a good time to bookmark a local air quality app or advisory source before you need it.
• Second trimester. Pooled studies flag first-trimester ozone exposure specifically, but pollution exposure across the whole pregnancy adds up toward the same small increases in preterm birth and low birth weight, so the same daily-check habit still matters here.
• Third trimester. Shortness of breath is already common in the third trimester, and poor air quality compounds it. Save strenuous outdoor activity for cleaner-air days and keep an N95 on hand for errands you cannot postpone.