Murder, birth and test scores: What scientists are learning about extreme heat

Heat waves have been linked to a higher risk of babies being born premature, as well as stillbirth. In California, researchers found that babies were more likely to be born before reaching full term if their mothers weathered an “extreme heat episode” in their last week of gestation.

“Heat acts like a trigger for preterm births,” said Tarik Benmarhnia, an environmental epidemiologist at UC San Diego’s Scripps Institution of Oceanography. Benmarhnia said scientists have suggested several possible mechanisms behind that result, including the effects of extreme heat on blood flow in the placenta, inflammatory response and dehydration.

Extreme heat has also been linked to a higher risk of pregnant patients suffering conditions such as preeclampsia and gestational diabetes, researchers have found.

And after a baby is born, Strehlow said, “it’s not clear if extreme heat decreases actual breast milk production or if just dehydration” is causing that result, he said, but it’s clear that when women face extreme heat and struggle to access cooling measures, they report that “breastfeeding suffers.”