Climate change has increased heatwaves and other extreme weather events. Scientists predict these will become even more common in the next decades. Heatwaves and rising average temperatures are major health threats, especially for people without the resources or money to respond to high temperatures. A large review of medical research shows that high air temperatures may harm pregnant women. For every rise of 1℃, there is an increased risk of premature delivery and stillbirth, especially in poorer women. These results suggest an urgent need to reduce heat exposure for pregnant women. The increase in heatwaves means that more pregnant women will be exposed to high temperatures. This may increase pregnancy complications, such as preterm birth and stillbirth. This study shows the need to reduce greenhouse gas emissions to lower air temperature.