A team led by Jasmin Abdel Ghany of Nuffield College, University of Oxford, published an analysis in the Proceedings of the National Academy of Sciences that draws on nearly three million births across 33 Sub‑Saharan African countries. Using geo‑referenced records from the Demographic and Health Surveys programme, the researchers matched individual pregnancies with local temperature conditions while accounting for socio‑demographic factors.
The main finding is a threshold effect in the first trimester: exposure to temperatures above 20 degrees Celsius was associated with an increased probability of biological pregnancy loss and a decline in male births. The authors relate this to the "frail male hypothesis", which proposes that male fetuses are more vulnerable to stress. The team also found that more extreme temperatures did not cause proportionally larger changes, suggesting the effect is triggered once heat passes a certain biological stress point. Women with lower education, older mothers and those in rural areas appeared particularly at risk.
The researchers compared results with births in India and observed a different pattern: second‑trimester heat exposure there was linked to fewer male births. The paper suggests this may reflect reduced access to or demand for sex‑selective abortions during hotter periods, a trend strongest in northern states.
Experts warn of limits to the analysis because Sub‑Saharan Africa is diverse in climate, health systems and culture; medical scientist Carl Chen noted that one region cannot represent the whole continent. The authors and other researchers argue that strengthening maternal and antenatal care, and scaled‑up investments to protect pregnant mothers from extreme heat, will be critical as climate change intensifies. This piece was produced by SciDev.Net's Sub‑Saharan Africa desk.
Difficult words
- threshold — point or level that causes change
- probability — chance that something will happen
- vulnerable — easily harmed or affected by stress
- antenatal — relating to care before a baby is born
- intensify — become stronger or more severeintensifies
- diverse — showing a range of different types
- match — bring together or compare two thingsmatched
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- Why might women with lower education, older mothers and rural residents be more at risk from heat during pregnancy? Give possible reasons.
- What practical steps could health systems take to protect pregnant women from extreme heat in your community or country?
- Experts warned that Sub-Saharan Africa is diverse. How does regional diversity make it difficult to apply one study's results to a whole continent?
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