Maternal exposure to outdoor air pollution associated with low birth weights worldwide

Mothers who are exposed to particulate air pollution, the type produced by vehicles and power plants, are more likely to bear children of low birth weight, according to an international study published today. The study was led by the University of California, San Francisco, and the National Center for Health Statistics at the Centers for Disease Control and Prevention.

Low birth weight is a risk factor for infant mortality, childhood illness and adult cardiovascular disease.

Study co-author, environmental health pediatrician Sheela Sathyanarayana, MD, MPH, of the University of Washington's School of Public Health and Medicine and Seattle Children's Research Institute, found modest effects on fetal growth in the Puget Sound Air Basin, a region in Washington state with low overall air pollutant concentrations. "Particulate Air Pollution and Fetal Growth was published in Environmental Health Perspectives.

The study, the largest of its kind ever conducted, analyzed data collected from more than three million births in nine nations at 14 sites in North America, South America, Europe, Asia and Australia. There are 29 authors from a variety of countries.

Research studies conducted in Los Angeles and New York City have identified high concentrations of air pollution as harmful to a developing fetus, but there have been few studies of traffic-related air pollution and birth outcomes in areas that have low to moderate air pollution. Sathyanarayana's study, as part of the large analysis, was the first in the United States to examine low level traffic-derived air pollutants in relation to small for gestational age birth.

Sathyanarayana and the research team also found associations between living within 50 to 150 meters of freeways and highways and an increased risk of small for gestational age birth. "The closer you live to a major highway or roadway, the larger the risk is for having a small for gestational age birth baby," she said.

Babies with small for gestational age birth may have problems at birth including decreased oxygen levels, hypoglycemia (low blood sugar) and difficulty maintaining normal body temperature. Up to 90 percent of babies born with small for gestational age birth catch up in growth by the age of two.

Parents or women considering a pregnancy should be aware that air pollution can affect health outcomes, based on the research. "If you are buying a house or renting an apartment and you have the choice, you may not want to live near a major highway," said Sathyanarayana.