Why doctors say pregnant people should be extra careful during a heat wave
Severe exposure to extreme heat can lead to preterm labour and stillbirths, experts say
With extreme heat and humidity creating dangerous conditions across the Greater Toronto Area, doctors are warning pregnant people about the serious health risks heat waves pose to them.
When temperatures soar above 30 C for several days, pregnant people are especially vulnerable to heat-related illnesses, says Dr. Tali Bogler, chair of family medicine obstetrics at Saint Michael's Hospital.
"We do have studies that have shown that there is certainly risk for the pregnancy and for both mom and baby," she told CBC Toronto.
Environment Canada says this summer's first heat wave is expected to create daytime highs of 33 to 36 C into Tuesday night, with humidex values of 42 to 46.
Bogler says that kind of heat can impact someone who's expecting, no matter what stage of pregnancy they're in.
During the first trimester of pregnancy, there is some limited evidence that shows prolonged heat exposure can result in congenital birth defects, she said, such as neural tube or heart defects.
In the second trimester, extreme heat can create issues around hypertension and gestational diabetes, and in the final trimester, it could result in a low birth weight, preterm delivery or stillbirths, Bogler said.
"The other piece is for people to be on the lookout if you're pregnant for symptoms of mild to moderate heat-related illness," she said.
If you get heat rash or feel unwell, get somewhere cool, but if you're experiencing more severe symptoms such as vomiting or feeling faint, then that should be treated as an emergency, Bogler said.
For pregnant people, staying hydrated means drinking about three litres of water a day or more, says Dr. Cynthia Maxwell, a maternal fetal medicine specialist at Mount Sinai Hospital.
"Because you're losing a lot of the moisture through the skin, and then of course, the requirements for the baby and for the circulation to the baby requires constant replenishment," she said.
Take precautions, experts says
Mom-to-be Julia Lee in Toronto is 23 weeks pregnant, and says she's been careful about how much time she spends outside.
"I've been really feeling it. I feel like summer came a little late, and then it kind of just hit us like a truck."
Because the heat wave is so intense and the risks so severe, it's important to take every precaution, says Dr. Modupe Tunde-Byass, associate professor of obstetrics and gynecology at the University of Toronto.
"Please stay indoors as much as possible. This is not the time to go [out] for exercise or extreme running," Tunde-Byass said.
"Stay hydrated, drink water [and] go to cooling centres, if you don't have an air conditioner."
Climate change worsening conditions, study finds
From 2020 to 2024, Toronto had 15 days of extreme heat risk for pregnant people, according to a recent study by non-profit Climate Central.
Its analysis found that of those days, half were added by climate change, says Andrew Pershing, the organization's chief program officer.
"Heat is only going to grow as a problem for us as we continue to burn coal, oil and natural gas and pollute the atmosphere with carbon dioxide," he said.
Pershing says he hopes the report can remind people of the realities of what's at stake when it comes to climate change.
"The longer we wait to act, the harder the problem gets to solve, and we've already waited a long time," he said.
"This is about keeping people safe."
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