A study published last week in the JAMA Network Open found that pregnant women who were exposed to higher temperatures and air pollution are more likely to birth babies that are premature, underweight, or stillborn.

“We already know that these pregnancy outcomes are worse for black women,” said Rupa Basu, the study’s co-author and chief of the air and climate epidemiological section for the Office of Environmental Health Hazard Assessment in California.

In examining 57 studies published since 2007, researchers found a clear relationship between birth outcomes in America and heat exposure as well as air pollution.

Researchers also found that exposure to higher rates of air pollution in the third trimester was associated with a 42 percent increased risk of stillbirth.

“Doing nothing about air pollution, which so clearly has a greater impact on Black Americans, is racism in action.”