Chimneys belch out smoke at the Beijing Capital Steel Plant , which has long been blamed as Beijing's worst polluter, on January 31, 2007 in western suburbs of the Chinese capital.
Credit: Andrew Wong

Beijing may have yet another reason to worry about its record-high air pollution.

A new study, published last week by Environmental Health Perspectives, found that exposure to high levels of polluted air increases a woman's chance of giving birth to an underweight baby. 

Called "Particulate Air Pollution and Fetal Growth," the UC Berkley-led study looked at the influence of air pollution on over 3 million infants born in nine different countries between the late 1990s and mid-2000s, according to the Daily Californian

With adjustments for various other factors, the researchers found that researchers found that low birthrate risk was between 10 and 15 percent higher in places where the air was most polluted in relation to those with the least polluted airspace. 

“Low birth weight has consequences later in life,” the study's lead author Dr. Payam Dadvand told the New York Times.

“Low birth weight babies are more likely to develop cardiovascular disease, diabetes and other illnesses, and more likely to die earlier. Low birth weight is one of the leading causes of morbidity and mortality worldwide," he added. 

The cities with the highest levels of air pollution in the study were Seoul and Sao Paolo; the lowest was Vancouver, according to the Daily Californian. 

“What makes the study unique is that the bulk of (air pollution) studies are on cardiovascular disease,” said Rachel Morello-Frosch, a study co-author and UC Berkeley professor. “Only recently have we started to look at birth outcomes."

"Mothers are a unique population that need to be taken into consideration," she added. 

Yet another reason to speed up action against pollution. 

More from GlobalPost: Beijing's air pollution reaches hazardous levels (UPDATES)

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