A systematic review and meta-analysis pooled 21 studies and 5,650 pregnancies complicated by gestational diabetes, comparing continuous glucose monitoring with self-monitored blood glucose. Risk of bias was rated low to moderate.
The glycaemic differences are modest. Mean blood glucose fell by 0.24 mmol/L (interval -0.41 to -0.06), coefficient of variation by 0.78 percentage points, mean amplitude of glycaemic excursions by 0.22 mmol/L, and time above 7.8 mmol/L by 2.19 percentage points. None of these would impress on their own.
The outcome differences are what matter: reductions of 8 to 35% across caesarean delivery, macrosomia, neonatal hypoglycaemia and hyperbilirubinaemia. Alongside them, a 21% increase in medication use.
That last figure is worth reading as mechanism rather than harm. A monitor that reveals postprandial excursions invisible to four daily fingerpricks leads clinicians to start or escalate treatment, and the treatment is what improves the outcomes. On that reading CGM is not a therapy but a case-finding tool for undertreatment — which suggests the benefit would be smaller wherever self-monitoring is already intensive and clinicians already escalate promptly.
- Includes observational studies alongside randomised trials
- The glycaemic differences are small; the outcome differences are not
- A 21% rise in medication use is likely the mechanism, not a cost
- Benefit should be smaller where self-monitoring is already intensive
- Cost and availability remain the constraint in most Indian units
The statistics, in plain English
A mean difference of -0.24 mmol/L with an interval from -0.41 to -0.06 excludes no effect but is a small shift in absolute terms. When small glycaemic differences accompany substantially larger outcome differences, the glucose measure is probably not the whole causal path — here the increase in medication use is the more plausible link, which matters because it means the benefit depends on clinicians acting on the data.
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