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Climate change may impact congenital heart defect risk
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Maternal heat exposure as a result of climate change appears to be increasing, with more intense and longer-lasting heat events projected in the United States by 2030. A new study has linked maternal exposure to extreme heat during the early weeks of pregnancy with increased risk for future congenital heart defects.
Researchers sought to identify the association between potential changes in heat exposure in pregnant women 3 to 8 weeks after conception and congenital heart defects.
“Prior studies have reported a positive relationship between extreme heat exposure and adverse reproductive outcomes, including preterm birth and low birth weight,” Wangjian Zhang, MD, PhD, from the department of medical statistics and epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China, and colleagues wrote. “Most importantly, two recent studies have reported an association between maternal heat exposure during early pregnancy and an increased odds of congenital heart defects, the most common birth defects grouping and a leading cause of infant morbidity and mortality in the United States.”
Lin and colleagues assessed data from the National Birth Defects Prevention Study, a multisite, large population-based case-control study that investigated risk factors for major structural birth defects in the United States.
The researchers defined multiple indicators of heat exposure and applied published ORs of congenital heart defects from baseline conditions from 1995 to 2005 into a projection period of 2025 to 2035.
The researchers projected increases in maternal heat exposure across all U.S. regions during the spring and summer, with a particularly high projected increase in the midwestern United States for summer maternal exposure to excessively hot days (OR = 3.42; 95% CI, 2.99-3.88 per pregnancy) as well as heat event duration (OR = 1.73; 95% CI, 1.49-1.97).
Lin and colleagues also identified an association between maternal heat exposure and specific congenital heart disease subtypes during spring, with greater increases in conotruncal congenital heart defect subtypes in the South (34% increase; 95% CI, 4.9-70.8) and atrial septal defect in the Northeast (38.6% increase; 95% CI, 9.9-75.1).
This study is the first to estimate future changes in maternal heat exposure and the associated burden on congenital heart defects, and the findings provide useful metrics and maps for policymakers involved in preparedness and resource allocation for climate change adaptation, according to the researchers.
“Exposure increases may be larger in summer, especially for the Midwest, followed by the Northeast and South regions,” Lin and colleagues wrote. “However, increases in the [congenital heart defect] burden can occur more in spring, especially in the South and Northeast regions for septal and conotruncal [congenital heart defects].” – by Earl Holland Jr.
Disclosures: The authors report no relevant financial disclosures.
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