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Topic Article
1. Cordero, Y., Mottola, M., Vargas, J., Blanco, M., & Barakat R. (2015). Exercise Is Associated with a Reduction in Gestational Diabetes Mellitus. Medicine and Science in Sport and Exercise, 47(7), 1328-1333. Doi: 10.1249/MSS.0000000000000547

What is the background to this research?
Gestational diabetes is a condition which arises during pregnancy and is characterised by high blood glucose levels1. Complications including pre-term birth, high blood pressure, and an increased risk of developing type II diabetes later in life can occur if the condition goes undiagnosed or untreated2. Researchers believe physical activity is the key to preventing, or reducing the prevalence of gestational diabetes because it assists in the metabolic control of glucose3. It does this by increasing the number of glucose transporters on a cells surface, resulting in improved glucose uptake into skeletal muscle, and decreased blood glucose levels1,4. However, there is currently minimal conclusive evidence to support the relationship between physical activity and the prevention of gestational diabetes5,6. A study by Cordero in 2015 increased the amount of reliable and valid evidence in this area by examining how a combination of aerobic and strength exercise can prevent gestational diabetes in women1.

Where is the research from?
The Technical University of Madrid in Spain provided the majority of funds for Cordero’s study1. The university also volunteered their facilities for the land based physical activity sessions. The Ministerio de Ciencia e Innovation in Spain contributed the remaining funds, and the Torreelodones Municipal Pool supplied facilities for the water based activities1. The completed study was published in the journal ‘Medicine and Science in Sports and Exercise’1.

What kind of research was this?
Cordero’s study was a randomised control trial consisting of a behavioural intervention1. The intervention comprised of supervised physical activity three times per week, one water and two land based sessions1. The randomised control trial is considered a level two research method by the National health and Medical Research Council, and is also the most appropriate design for clinical trials7. This means the results from the study provide strong evidence and support in regards to the relationship between physical activity and gestational diabetes prevalence.

What did the research involve?
Cordero’s study had 257 pregnant women complete the trial with a mean age of 33 years and a minimum of 80% compliance for the behavioural intervention. The women were divided into an intervention group and a control group. The intervention group participated in two 60min land based activity sessions, and one 50min water based activity session each week starting at 10-12 weeks gestation. Their intensity levels were monitored through Borgs scale of exertion, and heart rate measures. The control group were sedentary and only received usual antenatal care. The researchers were looking for changes to both primary and secondary outcomes. The primary outcome was the diagnosis of gestational diabetes, and secondary outcomes included excessive maternal weight gain, gestational age at delivery, delivery type, and birth weight and length1.

What were the basic results?
The results of Cordero’s study showed three significant differences between the intervention and control groups. These were…
 * 1) The intervention group had less diagnosed cases of gestational diabetes (1% compared to 8.8%)
 * 2) The intervention group had lower glucose values at the 180min mark in the fasted oral glucose tolerance test.
 * 3) The intervention group had fewer individuals with excessive maternal weight gain in accordance to their pre-pregnancy BMI (22.8% compared to 34.8%)

How did the researchers interpret the results?
Cordero’s study found the prescription of an aerobic and strength based exercise intervention decreased the prevalence of gestational diabetes. This finding contradicted the results from other level II research papers and a Cochrane review1,6. Cordero and those he collaborated with, believe their results differed because they initiated the intervention earlier in the pregnancy, <18 weeks gestation1. The Cochrane review included five studies, two of which initiated a physical activity intervention early within the gestation period. However, neither study found a significant difference between the control and intervention groups6. This suggests the intervention timing may not be the key to preventing gestational diabetes, and other factors should be explored. Cordero’s trial methods mimicked a study done in 2012 by Barakat, but there were two main differences within the methods. One, Cordero’s participants exercised for longer durations, and two, their heart rate did not rise above 60% of their estimated maximum in comparison to 70% in Barakat’s study1,8. Therefore, intensity or duration may be a significant factor in the prevention of gestational diabetes.

Cordero’s study examined several secondary outcomes and the intervention group showed significant differences in excessive maternal weight gain, and the metabolic control of glucose1. These findings support previous research which has shown improving these outcomes reduces the risk of developing gestational diabetes and type II diabetes1,9. Cordero also suggested that excessive weight gain influences the sensitivity of insulin increasing gestational diabetes risk, but the relationship between the two variables was not significant1.

What conclusions should be taken away from this research?
Cordero study has concluded there is a strong association between an aerobic and strength exercise intervention and prevention of gestational diabetes1. However, they believe the efficacy and effectiveness of the intervention is dependent on the compliancy rates of participants. Many studies have similar notions and exclude individuals who do not meet minimum requirements1,8. Cordero’s research confirms the association between physical activity, enhanced glucose metabolism and gestational diabetes intervention. They state participating in moderate exercise 3 times per week for a minimum of 50min, is effective in enhancing glucose metabolism and insulin sensitivity which reduces the prevalence of gestational diabetes1. Cordero identifies a lack of nutritional intervention or analysis as an important limitation to this research. This is because an individual’s nutrition can affect their insulin sensitivity and glucose metabolism. Therefore, not controlling or considering these factors may limit the reliability of Cordero findings.

What are the implications of this research?
Cordero’s study has provided an exercise intervention which successfully reduces the incidence of gestational diabetes and some secondary outcomes. This is important because few randomised control trials have developed successful exercise protocols showing significant differences1,6. The protocols employed by Cordero should be replicated with similar compliance rates, to ensure the results are valid and reliable. If successful, the intervention could significantly improve maternal health around the world, especially in at risk populations such as Indigenous Australians9. Cordero’s study may also stimulate further research because he identifies there is the lack of knowledge and specificity regarding effective interventions1.

Diabetes Australia
Web page: https://www.diabetesaustralia.com.au/managing-gestational-diabetes

Phone: 1300 136 588

The Royal Women’s Hospital
Web page: https://www.thewomens.org.au/health-information/pregnancy-and-birth/pregnancy-problems/pregnancy-problems-in-later-pregnancy/gestational-diabetes/