One study has shown that it can double the risk of miscarriages and stillbirths and make low birth weights more likely. The study’s authors are calling for updated heat advice for pregnant mothers globally. Half of them worked in high-heat environments such as farms, brick kilns or salt flats. The other half worked in cooler places, such as schools or hospitals. 6.1% who worked in extreme heat experienced premature birth or stillbirth against 2.6% from cooler workplaces.