According to the International Diabetes Federation (IDF), there was an estimated 199.5 million women with gestational diabetes mellitus (GDM) in 2015. This number is expected to rise to 313.3 million in 2030.

Statistics also showed that one in seven births is affected by gestational diabetes. To provide a closer look at the prevalence of GDM among pregnant women in Malaysia, the 3rd Report of National Obstetrics Registry (NOR) 2011-2012 stated that the incidence of diabetic pregnancy in Malaysia was 8.66% in 2011, and increased to 8.83% in 2012. As stated in the report, GDM rates are higher compared to pre-existing diabetes.

Relationship between outdoor temperature and GDM

A direct relation between ambient temperature and prevalence of GDM was revealed in a study by Gillian L. Booth and fellow researchers, in a study published in May 2017. In the study, researchers examined the co-relation between the mean 30-day outdoor air temperature before the time of GDM screening and the chances of diagnosis of GDM based on hospital records and physician service claims.

Based on the results, the prevalence of GDM was 4.6% among women exposed to extremely cold mean outdoor air temperatures (≤ -10°C) in the 30-day period prior to screening and increased to 7.7% among those exposed to hot mean 30-day temperatures (≥ 24°C). Furthermore, each 10°C increase in the mean 30-day outdoor air temperature was associated with 1.06 times higher odds of developing GDM.

Cold exposure and its effect on insulin sensitivity

Researchers also aimed to explore the relation between cool temperatures and the effect on human fat and metabolism. In a 2014 study led by Dr. Francesco S. Celi of Virginia Commonwealth University and Dr. Paul Lee at the Garvan Institute of Medical Research in Australia – participants were exposed to mild cold, neutral and warm temperatures for a month respectively, and for at least 10 hours each night.

The researchers found that following a month of exposure to mild cold, participants showed a 42% increase in brown fat volume and a 10% increase in fat metabolic activity. On the other hand, the alterations reversed during the month of being exposed to warm temperature. In addition, the increase in brown fat subsequent to a month of exposure to cool weather was accompanied by improved insulin sensitivity after a meal during which participants were exposed to mild cold.

In a different study conducted in 2016 by a group of researchers from the Netherlands, comprised of Dr. Lisanne L Blauw, found that glucose intolerance is found to be higher in warmer countries. The researchers concluded that a decrease in brown adipose tissue (BAT) activity with increasing environmental temperature may deteriorate glucose metabolism and therefore increase the incidence of diabetes.

Addressing climate change and pregnancy

The association between air temperature and the risk of developing GDM indicates the concern of how climate change can impact pregnancy. Climate change is also associated to many possible diseases and complications relating to maternal and newborn health.

Pregnant women are at risk of “over-heating” due to the hormonal situation at all stages of pregnancy – increasing the health risks for both mother and foetus. Considerable research effort is warranted to fill the knowledge gap on climate change and its effects on maternal and pregnancy outcomes.

In light of the discoveries made by previous research, modifying the thermal environment; for instance, by turning on the air-conditioner, or spending less time outdoors in hot weather, is necessary for pregnant women. Besides efforts such as counselling and universal screening for GDM – as recommended by the Malaysian National Obstetrics Registry – pregnant women should be informed that outdoor air temperature could influence the risk of developing GDM. MIMS

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