Air Pollution, Asthma and Pregnancy

Pregnant women may have increased risk of preterm birth if exposed to traffic-related pollutants.


The combination of asthma, pregnancy and air quality might lead to deadly consequences.

Researchers from the National Institutes of Health (NIH) found that air pollution exposure increased the risk of a preterm birth, a birth that occurs before the 37 week mark. The important time frames were prior to pregnancy, early in pregnancy and the last six weeks of pregnancy .

Asthma is a chronic lung disease that can cause wheezing, shortness of breath and coughing. Air quality is known to have an impact on people with respiratory conditions like asthma.

This study looked at the time frames of pollution exposure for pregnant women. It is the first study to establish that pre-conception exposure to air pollution can increase the risk of preterm birth.

"Preterm birth is a major public health problem in this country, affecting more than 1 in 10 infants born in the United States," lead author Pauline Mendola, PhD, said in a press release. "Our study found that air pollution appears to add to the preterm birth risk faced by women with asthma."

Dr. Mendola is an investigator at the NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development.

Dr. Mendola and her colleagues analyzed data of more than 223,000 women around the US. The women delivered single babies (no twins or multiples) between 2002 and 2008.

The researchers found pollutants from nitrogen oxides and carbon monoxide increased the risk of preterm birth in women with asthma. Both pollutants are common in automobile exhaust.

When women with asthma were exposed to increased nitrogen oxide in the three months prior to pregnancy, the risk of preterm birth climbed 30 percent, compared to 8 percent for women without asthma. Increased exposure to carbon monoxide increased the risk of preterm birth 12 percent for women with asthma, but did not affect women without asthma.

In the last six weeks of pregnancy, exposure to increased particulate matter also increased the risk of preterm birth in women with asthma. Particulate matter can include dust, acids and metals in the air.

Many communities track and report information on air quality, as does the Environmental Protection Agency. Women with asthma who are pregnant or contemplating pregnancy may want to limit outdoor activity if air quality is unhealthy.

The study was published in the March issue of the Journal of Allergy and Clinical Immunology.

Information on funding and conflict of interest was not available.