Review finds weak evidence favouring moderate blood sugar targets in diabetic women during pregnancy

Review finds weak evidence favouring moderate blood sugar targets in diabetic women during pregnancy

Women with diabetes are known to have a higher risk of adverse pregnancy outcomes, including birth defects and pre-eclampsia, compared with non-diabetic women.

NICE recommends that pregnant diabetic women aim for a fasting blood glucose between 3.5 and 5.9 mmol/litre and 1-hour postprandial blood glucose below 7.8 mmol/litre.

However, this guidance was issued in 2008 and is not clear about the evidence underlying the recommendation.  A new Cochrane systematic review set out to identify the optimal level for these targets during pregnancy.

Clinical question:

In diabetic women who are pregnant, what is the optimal level of glycaemic control to minimise the risk of complications?

The review included type 1 and type 2, but not non-diabetic women who developed gestational diabetes.    They looked at foetal and maternal outcomes.

The evidence:

Three trials were found, involving 223 women. The reviewers compared different combinations of treatment targets:  tight (≤ 5.6 mmol/L FBG); moderate (5.6 to 6.7); and loose (6.7 to 8.9).

They concluded:

In a very limited body of evidence, few differences in outcomes were seen between very tight and tight-moderate glycaemic control targets in pregnant women with pre-existing type 1 diabetes, including actual glycaemic control achieved. There is evidence of harm (increased pre-eclampsia, caesareans and birthweights greater than 90th centile) for ‘loose’ control.

Appraisal hints:

  • The reviewers only searched a register of clinical trials.  There may be other relevant research that has been published elsewhere.
  • Did the studies use the same definition of “tight”, “moderate” and “loose” glycaemic control?
  • There was not enough data to draw firm conclusions.  Further evidence is needed to clarify the optimal blood sugar targets in pregnancy.


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

Middleton P, Crowther CA, Simmonds L. Different intensities of glycaemic control for pregnant women with pre-existing diabetes. Cochrane Database Syst Rev. 2012 Aug 15;8:CD008540.

Douglas Badenoch
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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