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Exposure to extreme temperatures during pregnancy may impact infants' birth weight

Experts say outcomes were worse if the exposure happened in the second or third trimester

Pregnant woman sitting on couch in heat
Photo (c) isayildiz - Getty Images
A new study conducted by researchers from Bar-Ilan University explored how exposure to extreme temperatures may impact women during pregnancy. Their findings showed that experiencing severe hot or cold temperatures during pregnancy may increase infants’ risk of having a low birth weight. 

“Our study demonstrated the significant associations between exposure to high and low outdoor temperature and birthweight in all term births born in Israel during five years,” said researcher Dr. Keren Agay-Shay. “Lower birth weight may indicate abnormalities in intrauterine growth and is a risk factor for morbidity during early childhood and over the entire course of life.” 

Understanding pregnancy health risks

For the study, the researchers analyzed data from more than 624,000 births in Israel between 2010 and 2014. They also evaluated the residential areas where the women gave birth and tracked the temperatures throughout the women’s pregnancies. 

The researchers learned that exposure to extreme temperatures during pregnancy -- whether hot or cold -- increased the risk of infants being born with a low weight. Extreme cold temperatures were linked with a lower birth weight of 56g, while extreme hot temperatures were associated with a lower birth weight of 65g. 

The study found that these risks were the highest in the later months of pregnancy. Exposure to extreme weather in the second -- and even more so in the third -- trimester was associated with the biggest drop in birth weight. 

“The patterns of associations were consistent when stratified by urbanicity and geocoding hierarchy, when estimated for daily minimum and maximum temperatures, when exposures were classified based on temperature distributions in 49 natural regions, and when estimated for all live births (including preterm births and those with birth defects),” said Dr. Agay-Shay. 

Because global temperatures are predicted to continue going up, the researchers hope these findings lead to changes in public health strategies that address climate change. 

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