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.
Reference:
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.