Get proper prenatal care, and practice air pollution avoidance tactics.

Small start: Babies exposed to air pollution tend to be born with lower birth weights.

RODALE NEWS, EMMAUS, PA—Traffic jams and busy roadways may stunt your developing baby’s growth, says a new study published in the Journal of Epidemiology and Community Health.

THE DETAILS: Researchers studied birth certificates from 350,107 babies born in New Jersey between 1999 and 2003. All the babies were carried to term by mothers who lived less than 10 kilometers (about 6 miles) from a pollution monitoring station, where levels of carbon monoxide, sulfur dioxide, nitrogen dioxide, and particulate matter were measured. After controlling for pregnancy risk factors and socioeconomic influences, they found the chances of a woman having a smaller baby were higher when levels of nitrogen dioxide in the air spiked during her first, second, and third trimesters, and when levels of particulate matter went up during her first and third trimesters. Because nitrogen dioxide and particulate matter tend to come from traffic pollution, the researchers suggested that living near a major roadway or heavily trafficked area might be the primary culprit. They also found that higher pollution levels tended to make at-risk pregnancies more susceptible to late-term complications.

Pollution is certainly no friend to anyone, but it’s hard to pinpoint how these forms of pollution specifically affect pregnancy, says lead author David Rich, ScD, MPH, assistant professor in the Department of Epidemiology at the University of Medicine and Dentistry of New Jersey’s School of Public Health. “In the case of nitrogen dioxide, it may not be the actual bad actor. There may be other pollutants that come out of vehicles that are correlated to it.” Other studies have linked pollution, and specifically particulate matter, to low birth weights and fetal growth retardation, but as he found in his research, the exact pollutants and how they interfere with pregnancy are hard to pin down, Rich says.

WHAT IT MEANS: Avoiding outdoor pollutants during pregnancy seems to be more important than we knew. In addition to being at risk for learning difficulties, a study published last December found that babies born small were at a greater risk for developing type 2 diabetes later in life.

Here are a few ways to maintain a healthy pregnancy if you live near an area with lots of traffic pollution: