As Temperatures Rise, the Number of Male Births Is Decreasing, Study Finds
March 09, 2026 | Source: Euro News | by Marta Iraola Iribarren
As temperatures rise due to climate change, heat above 20°C leads to fewer male births, according to a new study.
When temperatures rise above 20°C, fewer baby boys are born compared to girls, a new study has found.
Researchers at the University of Oxford found that heat exposure can increase prenatal mortality in early pregnancy, particularly among males.
For many years, human sex ratios at birth – the ratio of male to female offspring – were thought to be constant, genetically determined, and invariant to social or environmental shocks, the authors wrote.
However, the results published in Proceedings of the National Academy of Sciences of the United States of America (PNAS) show that extreme heat may play a role in the number of boys and girls that are born worldwide.