The best way for pregnant women to protect themselves from this year’s summer heat is to simply stay indoors. In fact, officials are warning that this summer’s heatwave has become so severe that it’s become dangerous for senior citizens, children, pets, and yes, expectant mothers, too.

According to researcher Pauline Mendola, an epidemiologist at the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development, extreme temperatures during the various stages of pregnancy can increase the chances of preterm birth along with many other serious complications. The heat can also cause low birth weight in infants, according to a new study by a team of researchers at the National Institute of Health.

That’s why pregnant mothers are being urged to minimize their exposure to the sun, especially with the extremes temperatures that millions of people are dealing with all across the world.

The study looked at the results for hot temperatures in the 90 weather percentile. Yet, certain cities like Philadelphia experienced weather temperatures in the 98 weather percentiles, with this weekend expected to be even hotter.

Also, pregnant women are being urged to keep in mind that they need to keep out of the heat regardless of what stage of pregnancy they are in. The NIH researchers also found that women who were in their first seven weeks of their pregnancy during an extreme heatwave had about an 11 percent increase in risk of birth before 34 weeks and a 4 percent increase of a risky or complicated labor and delivery between 37 and 38 weeks.

The hot temperature outside isn’t the only problem for pregnant mothers-to-be. With that said, women who experienced extreme cold during the first trimester of their pregnancies were also more likely to have premature deliveries, including about a 20 percent higher risk of delivery before their 34 week of their pregnancy. Many pregnant women typically give birth anywhere between their 38 to even their 42 week of their pregnancy.

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Luckily, there are many ways that women can beat the heat. Staying inside a cool, air-conditioned home or apartment is one way while also drinking more water and keeping your food cool while also avoiding the use of an oven.