Heat linked to 855 extra premature births per million

A study of 36.6 million births across 13 countries found extreme heat increased preterm birth risk by 3.8%, with the effect most pronounced in the final weeks of pregnancy.

A study analysing 36.6 million births across 13 countries has found heat is responsible for 855 extra premature births per million births.

The research, published in Environment International, examined summer births in 250 towns and cities between 1979 and 2019. It found the risk of preterm birth increased by 3.8% on days of extreme heat.

The study covered births in Australia, Brazil, Canada, Chile, Ecuador, Estonia, Israel, Italy, Japan, Paraguay, Spain, Switzerland and the United States. Paraguay had the highest rate of heat-attributable preterm births at 1,347 per million, while Switzerland had the lowest at 628 per million.