Exposure to extremely hot weather raises pregnant women’s risk of severe health complications, researchers said in a study coming at the tail end of the warmest summer on record.
High outdoor temperatures during pregnancy were associated with a 27% increase in risk for such complications as sepsis, a potentially lethal reaction to infection, or dangerous increases in blood pressure, according to an 11-year review of more than 400,000 pregnancies in a Southern California health system.
July and August were the two hottest months on record globally, and the report Thursday in the journal JAMA Network Open highlights the dangers of hotter-than-normal weather that’s become more common as the earth warms. The trend threatens to worsen the US maternal mortality rate that continues to rise despite some of the highest health-care spending in the world.
The analysis of records from January 2008 through December 2018 compared the risk of complications among mothers who endured more extremely warm days during pregnancy with those who experienced fewer. The links between heat and risks of complications were greater among less-educated mothers than the rest of the population, an indication of the role of income and socioeconomic status in the effects of temperature, the authors said.
“Worse health outcomes among women with lower socioeconomic status may reflect the broader impacts of the persistent and pervasive social injustice issues,” the group of researchers from institutions in China and California said in the study.
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A number of factors may explain why high temperatures would be linked to complications, the researchers said. For example, loss of fluid in the body may contribute to the risk of sepsis. The strain of coping with high heat may also worsen underlying heart conditions, along with inflammation and inappropriate blood clotting, they said. Heart problems are among the leading causes of pregnancy-related deaths, according to data from the Centers for Disease Control and Prevention.
Pregnant people are more susceptible to extreme heat and may experience related exhaustion more quickly than others, according to the CDC. The report did not take into account people’s day-to-day behavior during pregnancy to include time spent indoors, for example, but the authors suggested that the availability of green spaces could ease the effects of extreme heat.
“Climate change will continue to impact all facets of health with increasing severity and duration of extreme heat events,” Anqi Jiao, an environmental health science doctoral student at the University of California, Irvine and first author of the study, said in an email. “It is important for individuals to take mitigation measures and increase their adaptability to extreme heat.”