Midwestern states could be most severely affected

Rising temperatures and extreme heat events associated with global climate change may have yet another important health impact: increased numbers of infants born with congenital heart defects (CHD). According to recent research conducted by a multi-disciplinary team that included University of Iowa investigators, heat waves in the United States over the next two decades may result in as many as 7,000 additional CHD cases between 2025 and 2035.

The study looked at climate change forecasts for eight representative states, including Iowa, and found that the greatest percentage increases in the number of congenital heart defects are predicted in the Midwest, followed by the Northeast and the South. Paul Romitti, professor of epidemiology in the UI College of Public Health, contributed to this research, which appeared in the Journal of the American Heart Association.

“Climate change may have a disproportionate impact on CHD in the Midwest,” said Romitti. “Our study predicts that this area of the country will potentially have the highest increase in maternal exposure to excessively hot days and heat event frequency and duration.”

Congenital heart defects are the most common birth defect in the United States, affecting some 40,000 newborns each year, according to the Centers for Disease Control and Prevention.

While previous research has found a link between maternal heat exposure and the risk for heart defects in offspring, the precise mechanisms remain unclear. Studies in animals suggest that heat may cause fetal cell death or interfere with several heat-sensitive proteins that play a critical role in fetal development, the researchers say.

The estimates in the current study are based on projections of the number of births between 2025 and 2035 in the United States and the anticipated rise in average maternal heat exposure across different regions as a result of global climate change. In their analysis, the researchers used climate change forecasts obtained from NASA and the Goddard Institute for Space Studies. They improved the spatial and temporal resolutions of the forecasts, simulated changes in daily maximum temperatures by geographic region, and then calculated the anticipated maternal heat exposure per region for spring and summer.

This study was supported by the National Institutes of Health and the Centers for Disease Control and Prevention, with partial support by the National Natural Science Foundation of China.