For pregnant people, extreme heat comes with extra risks

Doctors have long known that heat puts a strain on the heart, kidneys and other organs. Those risks are exacerbated for pregnant people, as the body's processes for staying cool are altered.

Doctors have long known that heat puts a strain on the heart, kidneys and other organs. Those risks are exacerbated for pregnant people, as the body’s processes for staying cool are altered.

It’s a problem that climate change, caused by the burning of fuels like gasoline and coal, is worsening. Intensifying extreme heat events, high temperatures well into the night and shattering weather records means more exposure for pregnant people, particularly in developing countries.

Here’s what to know about the science of pregnancy and extreme heat:

Pregnancy makes heat harder to handle

Pregnancy changes the body in myriad ways, which can make it more difficult and uncomfortable to dissipate heat.

“An obvious thing is, pregnant people have a belly bump, depending how far along they are, and that’s a change in their surface to volume ratio,” said Anna Bershteyn, an associate professor at New York University’s Grossman School of Medicine and director of Project HEATWAVE, an initiative aimed at improving research on preventing extreme heat deaths. Heat leaves your body through your skin, so when the belly gets larger, the heat has farther to travel to escape.

As pregnancy progresses, the body burns more calories, creating internal heat. The heart has to work harder, which can already be strained by extreme heat. And people who are pregnant also need more liquid to stay hydrated, so they might get dehydrated more easily, according to the Environmental Protection Agency.

One way the body cools itself is by shunting blood toward the skin and away from the central organs, which is why a person’s skin may flush and turn red when they get hot. Emerging research indicates that reduced blood flow to the placenta can affect the development of the fetus.