Absence of evidence on whether exercise can prevent gestational diabetes

A pregnant woman

Research has shown that light to moderate exercise during pregnancy is beneficial for mother and baby alike.  It has also been shown to prevent type 2 diabetes in men and non-pregnant women.  This Cochrane review looked at whether it can prevent diabetes in pregnant women.

Clinical question:

In pregnant women, does exercise prevent gestational diabetes?

The reviewers were interested interventions that advised and encouraged exercise as well as actually providing exercise sessions.

The evidence:

The reviewers found five trials comprising 922 women.  There was no evidence that exercise interventions reduced the incidence of gestational diabetes or insulin sensitivity.

The overall incidence of  gestational diabetes was around 6%.  This may be too rare an event for small studies to hope to detect a significant difference in outcome. However, the one large RCT (n=702) found no significant difference.

Appraisal hints:

  • The literature search was carried out in April 2012.
  • The studies were not of high methodological quality, suggesting that there is a high risk of bias in these findings.  The meta-analysis was dominated by one large trial.
  • We would expect there to be important differences between the interventions. They did not find enough data to perform meaningful sensitivity or subgroup analyses.
  • This is “absence of evidence” not “evidence of absence” of an effect of exercise on the risk of gestational diabetes.
  • More focused studies are needed, with greater methodological rigour, larger sample sizes and better outcomes reporting.


The full text of this review is available from the Cochrane Library.

Han S, Middleton P & Crowther CA.  Exercise for pregnant women for preventing gestational diabetes mellitus. Cochrane Database of Systematic Reviews 2012, Issue 7. Art. No.: CD009021. DOI: 10.1002/14651858.CD009021.pub2.

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I am an information scientist with an interest in making knowledge from systematic research more accessible to people who need it. This means you. I've been attempting this in the area of Evidence-Based Health Care since 1995. So far the results have been mixed. For some reason we expected busy clinicians to search databases and appraise papers instead of seeing patients. We also expected publishers to make the research freely available to the people who paid for it.. Ha! Hence The National Elf service.

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