Hot Weather Might Raise Your Gestational Diabetes Risk

Health Writer
Medically Reviewed

Gestational diabetes, the term used to describe diabetes that develops during pregnancy, has a host of risk factors. Now it appears that hot weather is also a hazard, according to a study published in the May 2017 Canadian Medical Association Journal (CMAJ).

Gestational diabetes affects more than 9 percent of women, according to a 2014 report by the Centers for Disease Control and Prevention. The condition can be dangerous for both mother and baby, which is why experts recommend pregnant women undergo screening between weeks 24 and 28.

The placenta, which carries nutrients to the growing fetus, secretes hormones that help the baby develop. But these hormones can also block the action of insulin on the mother’s body. The result can be hyperglycemia (high blood sugar); when it persists it is categorized as gestational diabetes. Risk factors include:

  • Family history of diabetes or gestational diabetes
  • Pregnancy after age 25
  • Previous birth to a large baby (over nine pounds)
  • Pre-diabetes
  • Obesity
  • Polycystic ovary syndrome (PCOS)
  • Excess weight gain during pregnancy
  • Hypertension
  • Sedentary lifestyle
  • Ethnicity (higher prevalence among African-American and Hispanic women, and women from South Asia and Southeast Asia)

According to the Canadian researchers, exposure to hot weather is also a risk factor. They found that the higher the outdoor temperature, the more significant the risk of developing gestational diabetes. In the study, researchers gathered data from women who gave birth in the greater Toronto area between 2002 to 2014. (Excluded from the study were women who gave birth prematurely, and women who had type 1 or type 2 diabetes prior to pregnancy.) By tracking over 550,000 births and looking at weather data obtained from Environment and Climate Change Canada, the researchers found a correlation between rates of gestational diabetes and temperatures charted for 30 days prior to diagnosis.

Overall, the rate of gestational diabetes was 6.5 percent among women having their first baby and 6.3 percent among women who’d given birth before. The researchers found that gestational diabetes occurred in 4.6 percent of women exposed to extreme cold for 30 days before the blood-sugar screening test. The rate increased to 7.7 percent in women who had been exposed to extremely hot temperatures for 30 days prior to the screening. With each incremental increase of 10 degrees, from extreme cold all the way to extreme heat, there was an additional 1.06 times higher risk of developing gestational diabetes.

The researchers suggest that prior studies that used PET scans to look at the impact of temperature on functional fat tissue (brown fat) showed that this metabolically active, insulin-sensitive tissue could be stimulated when participants were exposed to even brief “super cold” temperatures. Heat exposure seemed to evoke the exact opposite response in the pregnant women studied. If you add in other risk factors for gestational diabetes, hot weather may be the final nudge.

Limitations of the study included a lack of pre-pregnancy body mass index (BMI) measurements for all women in the database, as well as the absence of data on weight gain, fitness or activity level, or diet — variables that could have influenced the risk of developing gestational diabetes.

The research is timely given the ongoing discussions about global warming. If worldwide weather trends continue, the study suggests there may be an uptick in gestational diabetes. The findings also suggest that pregnant women may benefit by keeping indoor temperatures cool, spending time in the shade when outdoors during hot weather, and using cool compresses and fans after exercise or increased physical activity.

Here are other ways pregnant women can lower their risk:

See more helpful articles:

Obesity, Diabetes in Pregnancy Can Mean Dangerously Large Baby

Quiz: Could You Be Affected by Gestational Diabetes?