WASHINGTON – Pregnant women exposed to high temperatures or air pollution are more likely to have children who are premature, underweight or stillborn, and black mothers and babies are harmed at a much higher rate than the population at large, said sweeping new research examining more than 32 million U.S. births.

The research adds to a growing body of evidence that minorities bear a disproportionate share of the danger from pollution and global warming. Not only are minority communities in the U.S. far more likely to be hotter than the surrounding areas, a phenomenon known as the “heat island” effect, but they are also more likely to be located near polluting industries.

“We already know that these pregnancy outcomes are worse for black women,” said Rupa Basu, one of the paper’s authors and the chief of the air and climate epidemiological section for the Office of Environmental Health Hazard Assessment in California. “It’s even more exacerbated by these exposures.”

The research, published Thursday in JAMA Network Open, part of the Journal of the American Medical Association, presents some of the most sweeping evidence so far linking aspects of climate change with harm to newborns. The project looked at 57 studies published since 2007 that found a relationship between heat or air pollution and birth outcomes in the U.S.

The cumulative findings from the studies offer reason to be concerned that the toll on babies’ health will grow as climate change worsens.

Higher temperatures, which are an increasing problem as climate change causes more frequent and intense heat waves, were associated with more premature births. Four studies found that high temperatures were tied to an increased risk of premature birth ranging from 8.6% to 21%. Low birth weights were also more common as temperatures rose.

The authors looked at two studies that examined the link between higher temperatures and stillbirths. One found that every temperature increase of 1 degree Celsius in the week before delivery corresponded with a 6% greater likelihood of stillbirth between May and September. Both studies found racial disparities in the number of stillbirths.