Pregnant women exposed to higher levels of air pollution have babies who grow unusually fast, putting on fat that puts them at risk of weight problems later in life, new CU Boulder research suggests.

Women chronically exposed to pollution are known to deliver smaller babies. But in the first year, evidence suggests, they race to catch up, with that accelerated weight gain boosting risk of diabetes, heart disease and childhood obesity.

The researchers followed 123 Hispanic mother-infant pairs, periodically measuring the babies’ weight, height and fat distribution. They also tracked mothers’ prenatal exposure to the pollutants PM2.5, PM10, nitrogen dioxide and ozone.

Babies exposed to more air pollution prenatally had greater changes in weight and body fatness in the first six months of life.

Researchers believe the pollutants inflame mothers’ organs, influencing fetal development and affecting gene expression.

“Higher rates of obesity among certain groups are not simply a byproduct of personal choices like exercise and calories,” author Tanya Alderete said. “This study suggests it can also relate to how much of an environmental burden one carries.”