Warm temperatures in pregnancy linked to loss of male fetuses in Sub-Saharan Africa ^{CEFR B2}

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.