Freezing? Here’s why cold weather might be better for pregnant women

The weather might have taken a turn for the worse but that might not be a bad thing for expectant mamas...

Canadian researchers have just released their - slightly weird - findings that women who are exposed to colder temperatures during pregnancy have a lower rate of gestational diabetes than those exposed to hotter temperatures. Ok, this mum-to-be might be taking this advice to extremes but the study, published today in the Canadian Medical Association Journal, found that the prevalence of gestational diabetes was 4.6 percent among women exposed to extremely cold average temperatures (at or below -10C) in the 30-day period prior to being screened for gestational diabetes. This figure  increased to 7.7 percent among those exposed to hot average temperatures (above 24C). The study also found that for every 10-degree Celsius rise in temperature, women were six to nine percent more likely to develop gestational diabetes. The study examined 555,911 births among 396,828 women over a 12-year period. All the women studied lived in the Toronto area of Canada, but some were pregnant when the average temperature was warmer, and some when it was colder. Dr Gillian Booth, a diabetes researcher at St. Michael's Hospital, says that the findings might seem counterintuitive, but can be explained by emerging science about how humans make different kinds of fat:

"Many would think that in warmer temperatures, women are outside and more active, which would help limit the weight gain in pregnancy that predisposes a woman to 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."

Dr Joel Ray, who co-led the study, explains that a similar effect was seen for each 10-degree Celsius rise in the temperature difference between two consecutive pregnancies compared within the same woman:

"By further limiting our analysis to pregnancies within the same woman, we controlled for a whole number of factors. Doing so allowed us to eliminate factors like ethnicity, income, activity and eating habits that would differ between two different women."

In addition to a higher rate of gestational diabetes among women who were exposed to hotter temperatures during pregnancy, there was also a lower rate of gestational diabetes among Canadian women born in cooler climates versus those who were born in hot climates. Those women born in cooler climates, including Canada and the United States, and who were exposed to cold temperatures during the 30-day period prior to screening had a gestational diabetes rate of 3.6 percent, while those exposed to hot temperatures had a rate of gestational diabetes of 6.3 percent. In comparison, women who were born in hot climates, including South Asia, Africa and the Middle East, had rates of gestational diabetes of 7.7 and 11.8 percent, respectively. According to the research team, the findings, combined with the continued rise in global temperatures, could signal an increase in the future number of gestational diabetes cases worldwide:

"While changes in temperature of this magnitude may lead to a small relative increase in the risk of gestational diabetes, the absolute number of women impacted in Canada and elsewhere may be substantial. Gestational diabetes is new onset diabetes in the second trimester of pregnancy and is usually temporary, but the risk factors for gestational diabetes and adult onset type 2 diabetes are virtually the same. This is like the canary in the coal mine for the possible effects of global warming on adult onset diabetes."

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