Air Pollution During Pregnancy

Why pregnancy is a sensitive time

The American Lung Association describes pregnant people and their fetuses as being in a stage of life that is uniquely susceptible to harm from environmental contaminants, including air pollution. It explains that pregnancy is already a stress on the body, and that the extra inflammation and stress from polluted air can increase the risk of hypertensive disorders, including preeclampsia. It can also cause inflammation in the uterus and damage to the placenta that can disrupt the fetus's growth and development.^[2]

What the research links air pollution to

• Preterm birth, low birth weight and stillbirth. The American Lung Association says exposure to air pollution during pregnancy is strongly associated with premature birth, low birth weight and stillbirth.^[2]It also lists preterm birth, low birth weight, and fetal and infant mortality among the outcomes linked to year-round particle pollution.^[3]
• Particle pollution and birth weight. The National Institute of Environmental Health Sciences (NIH) reports that prenatal exposure to particulate matter was associated with low birth weight.^[4]
• Wildfire smoke. NIEHS describes a study of more than 5 million babies that found exposure to high levels of wildfire particulate matter during any period of pregnancy was associated with a greater chance of preterm birth.^[4]
• Traffic pollution and blood pressure. NIEHS cites a National Toxicology Program report that traffic-related air pollution increases a pregnant person's risk of hypertensive disorders, a leading cause of preterm birth, low birth weight, and maternal and fetal illness and death.^[4]
• Postpartum depression. NIEHS reports a study of more than 300,000 women that found long-term exposure to air pollution, especially ozone and PM2.5, during and after pregnancy increased the risk of postpartum depression.^[4]

These are associations found across large groups of people. They describe population risk, not what will happen in any individual pregnancy.

Which pollutant matters most?

Most of the findings above involve fine particle pollution (PM2.5), including wildfire smoke. The EPA says particles smaller than 10 micrometers can get deep into the lungs, and some may even get into the bloodstream.^[5]Note that the EPA's own list of groups most affected by particle pollution doesn't name pregnancy specifically,^[5] while the American Lung Association does treat it as a higher-risk stage of life.^[2]

Practical ways to reduce exposure

The EPA's general advice for cutting particle exposure applies to anyone:

• Check the AQI. Look at your local reading before spending long periods outdoors. Our city pages show current conditions.
• Avoid busy roads. Plan walks and commutes away from heavy traffic, and set car ventilation to "recirculate" on busy roads.^[6]
• Filter indoor air, especially during smoke events. Choose a portable air cleaner with a CADR large enough for the room. The EPA notes that HEPA filters often provide a high CADR.^[7]
• Skip ozone-producing cleaners. The EPA advises avoiding air cleaners that intentionally produce ozone, a lung irritant.^[7]

Ask your obstetrician or midwife about any specific concerns, such as wildfire smoke near you, a commute through heavy traffic, or an existing condition like asthma or high blood pressure.

What the AQI colors mean

AirNow reports the Air Quality Index (AQI) for five pollutants regulated under the Clean Air Act: ground-level ozone, particle pollution (PM2.5 and PM10), carbon monoxide, sulfur dioxide and nitrogen dioxide.^[1]

• Green, 0–50 (Good): air pollution poses little or no risk.^[1]
• Yellow, 51–100 (Moderate): acceptable, but there may be a risk for people who are unusually sensitive to air pollution.^[1]
• Orange, 101–150 (Unhealthy for Sensitive Groups): members of sensitive groups may experience health effects; the general public is less likely to be affected.^[1]
• Red, 151–200 (Unhealthy) and above: some members of the general public may experience health effects, and sensitive groups may experience more serious effects.^[1]

Check today's reading for your area on the city air quality pages or at AirNow.gov.