A study led by Jasmin Abdel Ghany of Nuffield College, University of Oxford, and published in the Proceedings of the National Academy of Sciences analysed nearly three million births across 33 Sub‑Saharan African countries. The researchers looked at temperature exposure during pregnancy and birth outcomes.
They report that exposure to temperatures above 20 degrees Celsius in the first trimester was associated with a higher likelihood of biological pregnancy loss, particularly for male fetuses. The authors link the pattern to the long‑recognised "frail male hypothesis", which holds that male fetuses are more vulnerable to stress in pregnancy.
The study describes a threshold effect: once temperatures rise above 20°C the probability of male births begins to decline, and more extreme heat did not produce proportionally larger changes. Women with lower educational attainment, older mothers and those in rural areas appeared especially at risk. Researchers used geo‑referenced Demographic and Health Surveys data to match pregnancies with local temperatures while accounting for socio‑demographic factors.
Experts note limits to pooling data across diverse countries, and the authors say further studies and stronger maternal health services will be needed as climate change intensifies.
Difficult words
- exposure — Contact with a condition such as temperature
- likelihood — Chance that something will happen
- pregnancy loss — End of a pregnancy before birthbiological pregnancy loss
- hypothesis — An idea or explanation to test
- threshold — A level where a change starts to happen
- rural — Related to the countryside, not the city
- maternal — Related to a mother during pregnancy or birth
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- What could stronger maternal health services do to help pregnant women during hot weather?
- Why might women with lower education or those in rural areas be more at risk from heat in pregnancy?
- How could rising temperatures affect pregnancies where you live, and what local actions might help?
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