In Pakistan’s Sindh, Dr Jai Das and his team at Aga Khan University (AKU) are leading the world’s largest study on the impact of extreme heat on pregnancy. Over 6,000 women will undergo detailed monitoring—including ultrasounds, temperature tracking, and placenta sampling—to uncover why rising temperatures are increasing risks for mothers and babies. With maternal and newborn deaths still claiming 4.5 million lives annually worldwide, the research could explain how climate change is worsening outcomes and slowing progress in reducing deaths during childbirth. The hope is that more research will reveal the physical processes whereby heat affects pregnancy outcomes, such as by altering bloodflow to the placenta, triggering hormonal changes or disrupting how foetal cells express certain genes.