Research Review:
Gestational diabetes… This won’t hurt a bit, trust me

Title: Exercise During Pregnancy Improves Maternal Glucose Screen at 24-48 weeks: A randomized controlled trial.
Author: Dr Barakat and colleagues (University Politecnica de Madrid, Spain)
Source: British Journal of Sports Medicine, 46: 656-661. 2012.

Introduction: In addition to my role as an accredited exercise physiologist, I am also a ‘diabetes educator’. After I found myself consulting so many diabetic patients, I completed a Graduate Certificate in Diabetes Education to keep me on top of my game.

As part of the requirement for the certificate, I was required to gain practical experience, which included hours spent with an endocrinologist (a doctor who specialises in diseases of the endocrine system, such as diabetes and thyroid disorders) at Manly Hospital in Sydney. It was tremendous to receive guidance and gain practical experience with a medical specialist in the Gestational Diabetes Clinic.

During this time, I was surprised by how few of the mothers-to-be knew what gestational diabetes was. Gestational diabetes occurs during pregnancy, and is believed to result from hormones from the placenta which block the action of insulin in the mother. This results in elevated blood sugar levels (hyperglycaemia). Risk factors for gestational diabetes include being overweight, family history of type 2 diabetes, previous history of gestational diabetes, and being aged over 30.

Generally, all mothers are screened at 24 to 28 weeks for gestational diabetes via an oral glucose tolerance test (a gold standard test for determining normal glycaemia, impaired fasting glucose, impaired glucose tolerance, type 2 diabetes and gestational diabetes). Ultimately, those mothers that are identified as hyperglycaemic (and unable to control their blood glucose levels via exercise and diet) are required to initiate insulin injections as they are not able to take oral tablets (oral hypoglycaemic agents).

To help reduce the likelihood of developing gestational diabetes in women who are pregnant, it is advisable for them to speak with their GP or obstetrician about the appropriateness of exercise.

"The exercise group had significantly lower (22.3 per cent) glucose and no incidence of gestational diabetes."

Methodology: Dr Barakat and his colleagues investigated the effectiveness of a cross-training physical activity program (land and aquatic sessions) in pregnant women. The land sessions comprised 25-minute core training followed by resistance training exercises (one set of 10-12 reps, light intensity). The aquatic sessions (water temperature 28 to 29oC) were designed to minimise impact and included swimming, walking/jogging in the water and using noodles.

A total of 83 pregnant women were randomised to either exercise or no exercise (control) groups. The average age of the mothers was 31.5 years, with all the mothers demonstrating normal BMIs (pre-pregnancy).

The exercise group completed supervised exercise sessions three times per week (35- to 45-minutes) for a total of 85 training sessions. Exercise training was initiated in weeks six to nine of pregnancy, and concluded at weeks 38 to 39. Subjects utilised heart rate monitors during all exercise sessions, with the training intensity consistently below 70 per cent of their age-predicted maximal heart rate (using the equation 220 – age). To maximise safety, participants worked in groups of 12 and were assisted by an obstetrician.

All subjects (exercise and non-exercise) completed 50 gram oral glucose tolerance tests. It is important to note that, according to the ‘Diabetes Management in General Practice’ (2011), pregnant women in Australia will be screened with either a 50 gram or 75 gram load.

The authors hypothesised that regular participation in exercise would lead to an improved maternal glucose tolerance, lower maternal weight gain and fewer cases of gestational diabetes.

Results: The exercise group had an impressive 85 per cent compliance to the exercise program. The women in the exercise group demonstrated less maternal weight gain (1.3kg) and had improved resting systolic blood pressures (4 per cent). Additionally, newborns from the exercise group were lighter (on average) by 61 grams.

With regard to the oral glucose tolerance test, the exercise group had significantly lower (22.3 per cent) glucose and no incidence of gestational diabetes, whereas the control group had three cases of gestational diabetes.

Pros: Great study, supports the benefits of appropriate low-intensity exercise during pregnancy to deter the onset of gestational diabetes. NB: every expectant mother, however, should be reminded to speak with their GP or obstetrician if they are going to either continue or initiate exercise during their pregnancy.

Women who are pregnant and contemplating exercise should read Sports Medicine Australia’s ‘Exercise during Pregnancy’ and ‘Exercise after Pregnancy’ fact sheet (http://sma.org.au/resources/policies/active-women/).

This is not the first exercise and pregnancy study that Dr Barakat has completed. Two years ago he investigated the effects of light-intensity exercise during pregnancy and found there were no adverse events during the exercise training period or delivery. In the exercise group, the majority (51) delivered naturally, while 10 required instruments and 11 a Caesarean section. The control/non-exercise group had similar results (50 natural, 9 required instruments, 11 Caesarean). The investigators concluded that progressive resistance training (in their study) did not alter the way a baby is delivered.

Cons: None.

Associate Professor Mike Climstein, PhD FASMF FACSM FAAESS
Dr Mike is the program director of Clinical Exercise Science at the Faculty of Health Sciences and Medicine at Bond University, QLD. He is recognised as one of Australia’s leading accredited exercise physiologists working with patients suffering from a wide array of chronic diseases and disorders. For more information on this, or any recent Research Reviews, email michael_climstein@bond.edu.au.

Joe Walsh, MSc
Joe is a highly experienced sport and exercise scientist, currently working as a principle investigator on a series of observational studies investigating the demographics of various cohorts of master athletes. Joe’s research interests include mathematical modelling, in particular use of Monte Carlo Methods and Markov Chains for modelling sports performance. He and Dr Mike have authored many scientific publications with findings presented at international conferences in Europe, Asia and North America.