• Posted September 8, 2023

Global Warming Could Make Pregnancies More Dangerous

Global warming has been linked to higher rates of asthma, heart disease and other health concerns. Now, new research suggests that rising temperatures across the planet may place pregnant women at greater risk for severe pregnancy-related illnesses, especially in their third trimester.

And this is likely to get worse in the near future, said study author Anqi Jiao, a Ph.D. student at the University of California, Irvine. “Climate change will continue to impact all facets of health with increasing severity and duration of extreme heat events,” she noted.

Severe maternal illness is an umbrella term for 21 serious conditions that can include heart attacks, kidney failure, sudden cardiac arrest, heart failure, anesthesia complications, blood infections, and need for a hysterectomy (removal of the uterus), among other illnesses and complications.

“These women… would have died without appropriate and timely identification and intervention, but severe pregnancy-related illnesses are thought to be preventable to a large extent,” Jiao said.

What's more, these conditions can result in longer-term treatment and recovery and place a greater financial burden on families, she added.

Exactly how exposure to extreme heat causes serious pregnancy complications for expectant moms is not fully understood, but the researchers have some theories. Heat exposure may lead to dehydration and an imbalance of minerals in the blood, which can cause inflammation, increased heart rate and other symptoms, Jiao said.

The study, published Sept. 7 in JAMA Network Open, included more than 403,000 pregnancies in Southern California from 2008 to 2018. Of these, there were 3,446 cases of severe pregnancy-related illnesses reported.

Women who had the most exposure to extreme heat during their pregnancy had a 27% greater risk for experiencing a severe pregnancy-related illness, and pregnant women who were exposed to extreme heat during their third trimester had a 28% increased risk for severe illness, the study showed.

Pregnant women with less education were also more vulnerable to heat exposure and related risks, the study showed.

“Doctors and society may provide more instructions or help them understand the potential heat effect during their pregnancy and encourage them to take action to prevent themselves from extreme heat,” Jiao said.

If you are pregnant during a heat wave, especially during the third trimester, take precautions to protect your health. This includes seeking shade when temperatures soar, Jiao said.

Dr. Nathaniel DeNicola has spent his career studying the effects of the environment on pregnancy outcomes in moms and babies. He is an obstetrician-gynecologist at the Caduceus Medical Group in Yorba Linda and Irvine, Calif. and the American College of Obstetricians and Gynecologists' environmental health expert.

The new study demonstrates that the timing of exposure to intense heat during pregnancy matters. “Extreme heat in the third trimester poses a greater risk for pregnant women, especially when it occurs in the week before delivery,” said DeNicola, who was not involved with the research.

Women who are in their third trimester during the true dog days of summer typically conceive from November through April, based on where they live, he said. Women who are in their third trimester during the winter months tend to fare better, he said.

There's lots to do to stay a few steps ahead of severe heat-related illnesses during pregnancy.

For starters, if you are pregnant during a heat wave, drink more water. “There is no exact amount of water that I recommend, but it's important to stay well ahead of thirst,” DeNicola said.

Look for ways to cool down during the day when the heat index is at its highest.

“If you don't have air conditioning where you live, consider cooling centers, museums or other public indoor spaces," DeNicola said.

He also tells pregnant women to download the U.S. Occupational Safety and Health Administration-National Institute for Occupational Safety and Health heat index app. “This app can let you know when it is safe to be outside or exercise outdoors and when it isn't,” he noted.

Know the signs of heat exhaustion, DeNicola added.

“These come on before heat stroke and can be subtle but accelerate rapidly,” he said. Signs include sweating, thirst, headache, muscle weakness, cramps, dizziness and nausea.

“These are early signs of heat exhaustion that tell you it's time to find ways to cool down,” DeNicola noted.

More information

Learn how to protect your heart during pregnancy.

SOURCES: Anqi Jiao, PhD student, public health program, University of California, Irvine; Nathaniel DeNicola, MD, chief medical officer, obstetrician-gynecologist, Caduceus Medical Group, Yorba Linda and Irvine, Calif., and environmental health expert, American College of Obstetricians and Gynecologists; JAMA Network Open, Sept. 7, 2023