Continuous Glucose Monitoring Feedback in the Subsequent Development of Gestational Diabetes: A Pilot, Randomized, Controlled Trial in Pregnant Women.

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• CGM during pregnancy may help women better understand their glucose patterns and increase awareness of lifestyle behaviours.

• Seeing real-time glucose results may improve motivation and satisfaction with monitoring, which may support healthier behavioural choices.

• CGM feedback alone may not be sufficient to reduce the risk of GDM.

• CGM may be a useful supportive tool during pregnancy but may need to be combined with additional nutritional guidance to influence positive outcomes.

Introduction

This pilot study compared gestational diabetes mellitus (GDM) rates and oral glucose tolerance test (OGTT) results between pregnant women using continuous glucose monitoring (CGM) with glucose feedback (unblinded) and those with masked data (blinded). Secondary aims were to assess feasibility and the impact of CGM feedback on glycaemic outcomes.

Methods

In this prospective, single-centre, pilot, feasibility randomised controlled trial, pregnant women in the first trimester were randomly assigned (1:1) to unblinded CGM with glucose feedback (n = 79) or blinded CGM (n = 87). GDM was screened at 24 and 28 weeks using a 75-g OGTT. The study followed CONSORT guidelines and evaluated feasibility, glycaemic measures and adverse events.

Results 

• There was no significant difference in GDM incidence between unblinded and blinded CGM groups (21.5% vs. 14.9%; relative risk 1.49, 95% CI [0.70–3.18]; p > 0.05).

• OGTT glucose values were similar between groups: fasting glucose 4.2 [IQR 4.0–4.5] vs. 4.3 [4.1–4.6] mmol/L (p = 0.48); 1-h glucose 7.7 [6.3–9.2] vs. 7.5 [6.3–8.7] mmol/L (p = 0.38); 2-h glucose 6.3 [5.8–7.7] vs. 6.2 [5.3–7.2] mmol/L (p = 0.15).

• Time in range (%TIR) was significantly higher in the unblinded group in the early-second trimester (88.7% [76.4–92.7] vs. 80.5% [59.6–90.4]; p = 0.02). Higher %TIR was also observed in the first trimester (p = 0.06) and third trimester (p = 0.07), but these were not statistically significant.

• Time below range (%TBR) tended to be lower in the unblinded group in the first trimester (15.4% vs. 21.2%; p = 0.06) and early second trimester (8.8% vs. 16.9%; p = 0.05).

• Adverse events occurred in 29.3% (unblinded) vs. 36.7% (blinded), mainly mild skin reactions at the site of sensor application.

Conclusion

CGM use during pregnancy was feasible; however, unblinded CGM feedback did not significantly reduce gestational diabetes rates.

• CGM use during pregnancy may be feasible and acceptable, with high user satisfaction reported.

• Providing real-time glucose feedback may increase engagement and perceived relevance of glucose monitoring.

• CGM feedback alone may not reduce GDM incidence, suggesting additional education and/or nutritional support may be needed.

• CGM may be considered as a supportive monitoring tool during pregnancy rather than a standalone prevention strategy.

• The small sample size limited statistical power, preventing definitive conclusions regarding the effect of CGM feedback on GDM development.

• Compliance challenges, including the need to scan the device every 8 hours and discomfort from sensor wear, may have influenced adherence and outcomes.

• Providing structured CGM education and personalised interpretation support may enhance behavioural changes and glycaemic control.

• Initiating CGM earlier, including preconception, may allow more time for lifestyle modification and improve glycaemic outcomes.