Temperatures Play Role in Gestational Diabetes

Warmer temperatures are affecting more pregnant women, study says.

An Ontario, Canada-based research team has found a connection between warm temperatures and gestational diabetes, the temporary condition that affects about 1 in 7 births worldwide.

Researchers from St. Michael’s Hospital, the Institute for Clinical Evaluative Sciences (ICES), Mount Sinai Hospital, and the University of Toronto found that every in 10-degree Celsius increase in temperature raises the risk of gestational diabetes in pregnant women by 6-9%.

The study, conducted over a 12-year span from 2002-2014, examined over 555,000 births from nearly 397,000 women in the Toronto area. The team set standards for cold outdoor temperatures at 10 degrees Celsius [50 degrees Fahrenheit] or less, and hot outdoor temperatures at 24 degrees Celsius [about 75 degrees Fahrenheit].

After exposing women to the differing temperatures for 30 days, the team screened them for gestational diabetes. While 4.6% of women exposed to cold temperatures were affected by the condition, the percentage jumped to 7.7% in women exposed to hot temperatures.

Results also reported a 1.06 times higher risk of gestational diabetes for every 10 degrees Celsius increase in temperature. There was a similar trend in results for women monitored for multiple pregnancies, which helped control some of the study’s moving factors.

Co-lead author and St. Michaels and ICES researcher Dr. Joel Ray, PhD, said analysis to pregnancies within the same woman allowed the research team to “eliminate factors such as ethnicity, income, activity, and eating habits that would differ between two different women.”

Though the study was limited to one geographical region, the researchers believe the results are likely to be generalizable worldwide.

The study is key in understanding a particularly unique condition. Gestational diabetes affects millions of pregnant women — oftentimes women with no prior history of diabetes. The blood sugar of affected women increases about midway through their pregnancy, when hormones in the placenta triggers insulin resistance. Previous studies have proven insulin sensitivity can be improved through exposure to cold temperatures.

Lead author and St. Michael’s and ICES researcher Dr. Gillian Booth (pictured), PhD, noted that many people would think warmer temperatures — which promote a more active lifestyle for pregnant women – would better limit weight gain and gestational diabetes.

“However, it fits a pattern we expected from new studies showing that cold exposure can improve your sensitivity to insulin, by turning on a protective type of fat called brown adipose tissue,” Booth said.

The authors warn that their findings mean that an even greater rate of gestational diabetes could occur over years as a consequence of global warming.

“Although changes in temperatures of this size may lead to a small relative increase in the risk of gestational diabetes mellitus, the absolute number of women affected in Canada and elsewhere may be substantial,” the study reads.

The study, “Influence of environmental temperature on risk of gestational diabetes,” was published in the Canadian Medical Association Journal.

A press release regarding the study was made available.

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