Professor Silva says pregnant women are also more vulnerable to the heat.
“When you're pregnant, your body is already working hard to keep you and your baby healthy, so adding the hard work of keeping cool can stress your body,” she says.
“Symptoms of overheating include warm skin, headache, dizziness, muscle cramps and nausea.
“Dehydration is one of the causes of Braxton Hicks, or so-called practice contractions, and it also can increase the incidence of dizzy spells and fainting.”
Professor Silva explains that doesn't mean pregnant women should avoid the outdoors.
“Activities out in the sun, in moderation, can have great health benefits including stimulating the body to produce more vitamin D, improving circulation, improving mood and reducing anxiety. Being in the sun also helps improve certain skin conditions and may help to increase the good bacteria in our bodies.
“Exercising is OK when precautions are taken. If women are going to exercise outside for long periods of time, we recommend that they stay well hydrated, wear loose-fitting clothing, and avoid high heat and humidity. Staying hydrated is one of the most important things.
“Pregnant women who feel they are overheating can move to a cooler place, sip water, loosen clothing, apply wet cloths to the skin, and sit in cool bathtub water. Those who experience vomiting or worsening symptoms that last longer than one hour should seek immediate medical treatment.”