Gestational Diabetes — Exercise reduces the risk for mother and foetus

Currently, Gestational Diabetes Mellitus (GDM) is the fastest growing type of diabetes in Australia. It affects between 12–14% of pregnant women and is usually diagnosed around the 24th to 28th week of gestation.

Correct exercise prescription alongside dietary modification will reduce the risk of developing GDM and provide help in the short- and long-term management of blood glucose levels (BGL).

Education on the what, how, when and who of exercise is vital to empowering pregnant women to make the right decisions.

Background

Pregnancy is a natural diabetogenic state for the purpose of increasing circulating BGL to provide an energy source available for the foetus.

The pregnancy hormones, progesterone and relaxin, also impact insulin resistance and beta cell function.

Insulin resistance in skeletal muscle is increased to leave more glucose available for the growing foetus; there is also decreased liver glycogen storage and elevated liver glucose release.

An increase in beta cell function occurs to help the cells create more insulin to keep up with increased demand of circulating BGL.¹

If a woman is insulin resistant prior to pregnancy, then additional changes caused by pregnancy hormones to insulin resistance will place more stress on the system, BGL can further elevate and GDM may be diagnosed.

GDM is classified as “any degree of glucose intolerance, such as hyperglycemia that is associated with insulin resistance and increased risk of cardiovascular pathology, with onset or first recognition during pregnancy.”²

If GDM is diagnosed and uncontrolled, it places the developing foetus at risk of macrosomnia, T2DM and childhood obesity, and the mother at risk of diabetes-related complications such as pre-eclampsia, obesity and obstetric complications, and they are 7–8 times more likely to develop T2DM postpartum.³

However, if it is managed there will be beneficial effects on both maternal and neonatal outcomes.

Treatment options

After diagnosis, usual treatment consists of glucose monitoring, and dietary and lifestyle modifications, such as exercise. These can improve insulin resistance and reduce BGL.

If these changes are not made or they are not successful in achieving adequate glucose control, then pharmacotherapy may be initiated to maintain euglycemia.⁴

Recently, Metformin has been utilised more frequently than insulin for GDM as it does not cause hypoglycemia or hyperinsulinemia.

Its primary mechanism of action is the reduction of hepatic glucose production, and secondarily it decreases intestinal absorption of glucose and improves insulin sensitivity by increasing peripheral glucose uptake and utilisation.⁴

Exercise

Exercise has similar mechanisms to Metformin; however, it has a greater ability to reduce postprandial blood glucose and there is strong evidence to support using exercise as a therapeutic adjunct for women with GDM.

An acute session of exercise increases the action of insulin by stimulating glucose uptake in muscles, activates intracellular glucose transporters, increases the use of intracellular fatty acids and alters the expression of muscle proteins involved in insulin responsiveness — consequently, regulating glucose metabolism and decreasing BGL for up to 72 hours after exercise.⁶

The long-term benefits are reduced fasting BGL and HBA1c levels, when compared to standard care.⁶

Better control of glucose metabolism is seen in women who exercise compared to those who remain sedentary, both in healthy pregnant women and in pregnant women diagnosed with GDM,⁷ suggesting exercise as a preventative therapy.

Why should we use exercise over (or adjunct) to pharmacotherapy?

Because it helps long-term and short-term outcomes by lifestyle modification to reduce the risk of ante-natal, peri-natal and post-partum complications — not just bandaiding during pregnancy.

An Accredited Exercise Physiologist (AEP) is the best allied health practitioner to assist with exercise prescription for GDM.

Pregnant women diagnosed with insulin resistance or GDM need both structured aerobic training and resistance training.

Guidelines stipulate exercising for 30 minutes at a moderate intensity on 5 or more days per week, much the same as for the healthy population; however, specific care needs to be taken with exercise prescription for women with GDM.

AEPs are the experts on the physiological effect of exercise on chronic conditions. They understand how, when and why the body will best respond to exercise and what type is most suited.

In GDM, the timing of exercise in relation to pharmacotherapy and food intake is of upmost importance for the safest and most beneficial result.

Pregnancy also comes with many other musculoskeletal, metabolic, cardiovascular and psychological considerations that an AEP is well equipped to work with.

Each woman and her pregnancy is different and a Women’s Health Exercise Physiologist is even better equipped to work with women in pregnancy.

Take home points:

• GDM diagnosis is on the rise.
• GDM patients are 7–8 times more likely to develop T2DM post-partum.
• Exercise works the same as Metformin and is even more effective at reducing postprandial BGL.
• AEPs are best positioned to prescribe exercise for GDM, also taking other barriers, pharmacotherapy and musculoskeletal pain into consideration.

Naomi Goessling, Accredited Exercise Physiologist & Women’s Health Expert

 References

1. Gillman, M. W., Rifas-Shiman, S., Berkey, C. S., Field, A. E., & Colditz, G. A. (2003). Maternal gestational diabetes, birth weight, and adolescent obesity. Pediatrics, 111(3), e221–e226.
2. Catalano, P. M., Huston, L., Amini, S. B., & Kalhan, S. C. (1999). Longitudinal changes in glucose metabolism during pregnancy in obese women with normal glucose tolerance and gestational diabetes mellitus. American journal of obstetrics and gynecology, 180(4), 903–916.
3. Claesson, R., Åberg, A., & Maršál, K. (2007). Abnormal fetal growth is associated with gestational diabetes mellitus later in life: population-based register study. Acta obstetricia et gynecologica Scandinavica, 86(6), 652–656.
4. Reece, S.W., Parihar, H.S. & Lobello, C., 2014. Metformin in Gestational Diabetes Mellitus: Table 1. Diabetes Spectrum, 27(4), pp.289–295.
5. Harrison, A.L. et al., 2016. Exercise improves glycaemic control in women diagnosed with gestational diabetes mellitus: a systematic review. Journal of Physiotherapy, 62(4), pp.188–196.
6. Kokic, I.S. et al., 2018. Acute responses to structured aerobic and resistance exercise in women with gestational diabetes mellitus. Scandinavian Journal of Medicine & Science in Sports.
7. Cordero, Y. et al., 2015. Exercise Is Associated with a Reduction in Gestational Diabetes Mellitus. Medicine & Science in Sports & Exercise, 47(7), pp.1328–1333.