According to recent findings, exposure to high amounts of certain pollutants found in traffic air might increase the risk of preterm birth in women with asthma.

The study, published in the Journal of Allergy and Clinical Immunology demonstrates that both short-term and long-term exposure to traffic air pollutants are contributing factors. Moreover, asthmatic women who were exposed to these pollutants just prior to conceiving, during early pregnancy and in the last six weeks of pregnancy were at a significantly higher risk of preterm birth.

Preterm Birth – Major Public Health Problem

Preterm birth is defined as the birth of an infant before 37 weeks of pregnancy. One in every 10 infants born in the US is preterm, as stated by study author Pauline Mendola, an investigator at the US National Institute of Child Health and Human Development. Simultaneously, asthma affects approximately nine percent of all US women of reproductive age. Asthma is a known risk factor for pregnancy complications and health complications in infants.

Despite evidence associating ambient (outdoor) air pollution with mortality and respiratory morbidity over the past 30 years, researchers have recently began to investigate its impact on the cardiovascular system and pregnancy outcomes.

The tenure of pregnancy might consist of a period during which fetal development is particularly susceptible to toxins present in air, leading to increased cell proliferation and altering the capabilities of fetal metabolism. Also, the well-established link between adverse birth outcomes and maternal smoking provides support to claim that outdoor air pollution could play a potential role in complicating pregnancies.

Study Findings

Data from 223,000 single-child births between 2002 and 2008 was analyzed, which included babies born in 19 hospitals across the US. Researchers also assessed the quality of air from the regions around these hospitals. Six types of pollutants were measured, including carbon monoxide and nitrogen oxide.

According to the findings, increased exposure to nitrogen oxide three months before pregnancy was linked to an increased risk of preterm birth. More importantly, this risk was higher in women with asthma as compared to those without the disease.

Carbon monoxide exposure three months prior to pregnancy increased the risk of preterm birth by 12 percent for asthmatic women, and was found to have no effect on healthy women.

Furthermore, exposure to increased amounts of particulate-matter air pollution (tiny particles of dust, metals and acids) was also linked with a higher risk of preterm birth in asthmatic women.

Possible Explanation For Findings

“Early-on environmental exposures can have significant effects on future health”, highlighted Mendola. She added that such an exposure may trigger the onset of inflammation and other internal stresses. The latter could hinder fetal development and cause preterm birth, especially among women with asthma.

“These findings set the stage for future studies designed to help prevent preterm birth in this at-risk group”.


Since fetuses are highly susceptible, the disruption of development will have a significant impact on their overall health and well-being way into adulthood. Millions of women are exposed to air and traffic pollution on a daily basis and it’s about time that more pre-cautionary measures were adopted to reduce the adversities attributed to this nuisance.

Despite reporting a strong association between traffic pollution and preterm birth in asthmatic women, the study does not establish a cause-and-effect relationship. Some affirmative action will be needed when enough data will ultimately be accumulated in this regard. Nevertheless, health organizations must bring formulating set standards and policies to reduce the occurrence of mortality and respiratory diseases attributed to air traffic pollution.