Gestational diabetes mellitus (GDM) appears to be on the rise
in the US, with the CDC suggesting that the prevalence of GDM may be as high as
9.2% (http://www.cdc.gov/pcd/issues/2014/13_0415.htm). The disease is defined as the onset of impaired
glucose intolerance during pregnancy as diagnosed from a glucose screening test (also called a
glucose challenge test or GCT) between 24 and 28 weeks of pregnancy. Pregnant
women who develop GDM are at a higher risk complications during pregnancy and
delivery, and the fetus may develop macrosomia, neonatal hypoglycemia, In
addition, women who develop GDM have a greater than 7-fold increased risk of
developing type 2 diabetes later in life. There’s some suggestion that babies
born to mothers with GDM have a greater risk of developing impaired glucose
tolerance.
What impact may exercise during pregnancy have on the development of this disease? There’s been an increase in the number of studies that have looked at the impact of prenatal exercise on the development of GDM, as well
as how exercise may help with the treatment in women who have it. Recent data
suggests that exercise during pregnancy may positively impact the development
and treatment of GDM, but the results are somewhat mixed, and may be due to the
quality of the studies and type, intensity and duration of the fitness
programs.
A Cochrane Review (considered a key resource in evidence-based
medicine) reviewed randomized and cluster-randomized trials assessing the
effects of exercise for preventing pregnancy glucose intolerance or GDM and
found that conclusive evidence is not available to guide practice (Cochrane Database Syst Rev. 2012 Jul 11;7:CD009021.). They suggest that more well-designed randomized trials, with standardized behavioral interventions are
needed to assess the effects of exercise on preventing GDM and other adverse
pregnancy. Other studies (Med Sci Sports Exerc. 2014 Oct 20., Br J Sports Med.
2013 Jul;47(10):630-6.) have concluded that exercise does reduce the incidence
of GDM, and may play a role in the development of type 2 diabetes in women who
had GDM (Best
Pract Res Clin Obstet Gynaecol. 2015 Jan;29(1):110-22.).
The bottom line? The inclusion of an exercise program during
pregnancy may be a positive step towards reducing the incidence of GDM, but we
still don’t know what exercise threshold is needed to maintain or improve
glucose tolerance. A reasonable prescription would be to set intensity levels
at a moderate to somewhat hard level on the Borg scale (not so high that the
woman is out of breath or feels discomfort) and allows her to maintain a duration
of at least 30 minutes, 5-6 days a week. I suspect that maintaining a higher
frequency (near 6 days a week) may play a greater role in maintaining normal daily
glucose tolerance, so the exercise intensity should be modified to enable her
to maintain >30 minutes of exercise at least 5 days a week. The type of
exercise should be one that is comfortable and easily modified throughout
pregnancy, and if possible be weight bearing.
Do you have any experiences working with GDM?
Feel free to post your comments and questions.
Key
words:
Fetal
Macrosomia: Fetal macrosomia
is a term used to describe a newborn who's significantly larger than average.A
baby diagnosed with fetal macrosomia has a birth weight of more than 8 pounds,
13 ounces (4,000 grams), regardless of his or her gestational age. Fetal
macrosomia makes vaginal delivery difficult and puts the baby at risk of injury
during birth and increased risk of health problems after birth.
Neonatal
hypoglycemia: Neonatal hypoglycemia, defined as a
plasma glucose level of less than 30 mg/dL (1.65 mmol/L) in the first 24 hours
of life and less than 45 mg/dL (2.5 mmol/L).
Gestational
diabetes mellitus (GDM): A disorder
characterized by an impaired ability to metabolize carbohydrates, usually
caused by a deficiency of insulin or insulin resistance, occurring in
pregnancy. It disappears after delivery of the infant but, in a significant
number of cases, returns years later as type 2 diabetes mellitus. Treatment
consists of self-monitoring of blood glucose, insulin administration, increased
activity, and a meal plan that controls the amount of carbohydrates eaten.
Impaired
glucose tolerance: Impaired glucose tolerance (IGT) is a pre-diabetic state of hyperglycemia that is
associated with insulin resistance and increased risk of cardiovascular
pathology. IGT may precede type 2 diabetes mellitus by many years.
Cochrane Reviews: A database of systematic reviews and meta-analyses which
summarize and interpret the results of medical research. The Cochrane Library
aims to make the results of well-conducted controlled trials readily available and is a key resource in evidence-based medicine.
