Gestational diabetes may increase with warmer days, study finds

— -- Diabetes during pregnancy has long frustrated doctors trying to discern why some women are more at risk for the disease than others. Though some factors have been associated with increased risk for the condition, including age, family history, excess weight and race, many questions remain.

A new study published today in the Canadian Medical Association Journal looked at 396,828 pregnant women and found another potential factor that could increase the risk for gestational diabetes: rising temperatures.

"There is also growing evidence supporting a link between air temperature, metabolic function and energy expenditure," the authors wrote.

Researchers at the Mount Sinai Hospital, University of Toronto and St. Michael's Hospital in Toronto, studied 555,911 births from women in the Toronto area between 2002 and 2014 to see if certain temperatures were associated with increased risk of gestational diabetes.

They studied the average temperatures for 30 days before a pregnant woman's routine test for gestational diabetes, which occurs at 27 weeks.

They found that the prevalence of women diagnosed with gestational diabetes was higher if there the weather was warmer shortly before they were diagnosed. When the average temperature was above 24 degrees Celsius, or about 75 degrees Fahrenheit, approximately 7.7 percent of women were diagnosed with gestational diabetes. When the average temperature was below -10 degrees Celsius, or about 14 degrees Fahrenheit, just 4.6 percent of pregnant women studied were diagnosed with the condition.

"If the association between air temperature and risk of gestational diabetes mellitus is real, then modifying the thermal environment (e.g., lowering the setting on a home thermostat or spending more time outdoors in cooler weather) may reduce risk of gestational diabetes mellitus," the authors concluded.

Previous studies have found that cold temperature can have major changes on how the body processes fat and adipose tissue. Cold temperatures are associated with an increase of "brown fat" in the body, which can improve glucose levels and metabolism, according to at least one published study by the National Institutes of Health.

Dr. David Hackney, Division Chief, Maternal Fetal Medicine at UH Cleveland Medical Center, said the study was interesting and joins a growing number looking at how temperature can affect effect the body's metabolism.

It's an "area of concern due to issues regarding rising temperatures and global warming," Hackney said. "We're starting to see a rising number of studies across a number of different fields."

This study is a start. He said that far more research would need to be done to correlate simple temperature changes to rates of gestational diabetes. There may be several factors that could create the relationship.

"As the temperature changes, maybe they go outside less or there's impacts on activity levels or changes in particles of the air," Hackney said.

Gestational diabetes is associated with a host of birth complications. Some fetuses can become extremely large in the womb and become injured during the birthing process or an emergency cesarean section may be required to safely deliver the baby.

Newborns with mothers who had gestational diabetes may also suffer from low blood sugar immediately after delivery. Hackney said there are concerns they could be at increased risk for metabolic issues as they grow older.

For women, having gestational diabetes can increases risk for type 2 diabetes even years after giving birth.