Pregnant in the summer? You're at greater risk for gestational diabetes

When the temperature rises, so does your blood sugar, and that could lead to gestational diabetes when you’re pregnant says a new study.

Pregnant woman with a bicycle
Photo: iStockphoto

You’ve probably realized that being pregnant in the summer means you’ll be sweating extra profusely on those sweltering days and gazing enviously as others sip mojitos on the patio while you drink water in between frequent pee breaks. But did you know that being pregnant when it’s hot out also increases your risk for developing gestational diabetes?

Gestational diabetes is a condition that occurs during pregnancy in which your body can’t produce enough insulin to keep blood sugar at a normal level. Though it typically doesn’t show any noticeable symptoms, it can cause women to have bigger babies, leading to interventions like C-sections during delivery, and it’s associated with a higher risk of developing type 2 diabetes later in life.

The news that gestational diabetes could be influenced by temperature came from a Toronto-based study that looked at more than 550,000 births from nearly 400,000 moms. Women are typically screened for diabetes 27 weeks into pregnancy. Researchers decided to compare the average temperature in the 30 days before that point to see if there was a relationship between the outdoor temperature and the diagnosis of gestational diabetes.

The study, which was published in the Canadian Medical Association Journal, found that 6.5 percent of women experienced gestational diabetes during pregnancy, but, among those who experienced temperatures -10 degrees Celsius or colder, only 4.6 percent had the condition. Meanwhile, among those who were sweating it out at 24 degrees Celsius or more, the rate of gestational diabetes rose to 7.7 percent.

Researchers concluded that every 10-degree-Celsius increase is associated with a six to nine percent relative increase in a woman’s risk. And when individual women had more than one pregnancy, researchers were able to observe similar results in separate pregnancies that occurred at different times of year, which helped to control for other factors, such as ethnicity or lifestyle habits.

The reason your risk rises with the temperature? Evidence shows that a layer of brown fat that lies just below the skin and is used to heat the body in cold temperatures can actually increase insulin sensitivity, which offers some protection against diabetes.

“As the season gets colder, you’re going to develop more brown fat,” says Dr. Gillian Booth, an endocrinologist and researcher at St. Michael’s Hospital in Toronto and one of the study’s lead authors. She adds that, in some studies, simply turning down the thermostat a few degrees can show improvements in insulin sensitivity, and some researchers are looking at the benefits of cold temperatures for increasing brown fat and promoting weight loss. Because body weight before pregnancy and weight gained during pregnancy are important to determining your likelihood of developing gestational diabetes, anything that keeps extra pounds off can offer a big advantage.

Though researchers have been interested in the powers of brown fat for a while, the results of this study are still surprising. “We know that Canadians are less active during wintertime so we would think women would be worse off in the winter, but we found the cold temperatures were actually protective,” says Booth.

Want to reduce your chance of developing gestational diabetes? If it’s winter, get outside and go for walk. Booth says the activity can lower your risk by helping to control weight and blood sugar, plus, exposing your body to the cold can be protective. As for those hot and sticky days, Booth says, “It’s still good to be active. You might look for opportunities to walk in air-conditioned areas. Walking is still important and you shouldn’t avoid the outdoors because of the heat.”

If you’re feeling worried—and a little sweaty—during your summer pregnancy, you can also limit weight gain by avoiding sugary foods and beverages, to lower your risk. And you can also turn down the thermostat, no matter the time of year. The good news? Now you have another bargaining chip to crank up the AC, even after your partner has had to put on a sweater.

Read more: 
How to manage gestational diabetes
5 ways to beat the heat while pregnant

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