(CNN) - Something most pregnant women don't think much about could be harming their babies: the temperature.
A new study says more children are likely to be born with heart defects because of global warming.
The study published in Wednesday’s “Journal of The American Heart Association” forecasts climate change could cause 7,000 cases over an 11-year period.
"The potential increases in both the number of pregnant women and maternal heat exposure suggest an alarming effect that climate change may have on reproductive health," the study said.
Scientists aren't sure why exposure to high temperatures seems to cause heart problems.
Animal studies have found heat can cause fetal cell death and harm proteins necessary to development.
"Our findings underscore the alarming impact of climate change on human health and highlight the need for improved preparedness to deal the anticipated rise in a complex condition that often requires lifelong care and follow-up," said study author Dr. Shao Lin, a professor in the School of Public Health at the University of Albany. "Although this study is preliminary, it would be prudent for women in the early weeks of pregnancy to avoid heat extremes similar to the advice given to persons with cardiovascular and pulmonary disease during heat spells."
Women who are pregnant during the spring or summer months in warmer climates are at the most risk.
All of the US is expected to face warmer temperatures in the future.