The effects of climate change are already being felt across the globe from melting icepacks and glaciers to raging wildfires and floods. But scientists now say there is another sobering impact looming: Increasing temperatures and more extremely hot days will cause more infants to be born with congenital heart defects in the United States over the next 20 years.

Researchers at the State University of New York looked at data from the National Birth Defects Prevention Study and information from Goddard Institute of Space Studies and projected that between 2025-35, congenital heart defects could more than double in the Midwest. Substantial increases were also predicted for the Arkansas-Texas region and the Northeast, according to a report published in the Journal of the American Heart Association.

How do rising temperatures impact pregnancies? The researchers said exposure to extreme heat during early pregnancy can cause fetal cell death or interfere with protein synthesis and induce fetal malformations that have been observed in animal studies. As global temperatures rise, more intense and long-lasting heat events are expected.

The study found more frequent springtime extreme heat events in the South would lead to a nearly 13 percent rise in overall congenital heart defects. Pregnant women have been shown to be more susceptible to the adverse effect in the spring.

The authors acknowledged limitations to their study, such as whether and how the population will begin adapting to the rising heat levels. But they called on clinicians, especially obstetricians, to advise pregnant women to be cautious about extreme heat exposure during the early stages of their pregnancy.