CGM Metrics and the Risk of Pregnancy Complications in Type 1 Diabetes: A Secondary Exploratory Analysis of the CRISTAL Trial
Ina Geerts, Kaat Beunen, Liese Berger, Nancy Van Wilder, Dominique Ballaux, Gerd Vanhaverbeke, Youri Taes, Xavier-Philippe Aers, Frank Nobels, Liesbeth Van Huffel, Joke Marlier, Dahae Lee, Joke Cuypers, Vanessa Preumont, Sarah E. Siegelaar, Rebecca C. Painter, Annouschka Laenen, Pieter Gillard, Chantal Mathieu, Katrien BenhalimaObjective:
To examine the associations between continuous glucose monitoring (CGM) metrics, including glucose management indicator (GMI) and overnight glucose levels, and pregnancy outcomes in women with type 1 diabetes.
Research Design and Methods:
Secondary exploratory analysis of the CRISTAL trial including 95 pregnant women with type 1 diabetes using CGM. Associations were assessed using logistic regression and Spearman correlations, presented as odds ratios (95% confidence intervals [CIs]) adjusted for baseline HbA1c. GMI validity was assessed using scatter and Bland–Altman plots.
Results:
Each 5% increase in overall pregnancy-specific time-in-range (TIRp) decreased the odds of gestational hypertension (odds ratio [OR] 0.63, 95% CI 0.41–0.97), birthweight >4.5 kg (OR 0.56, 95% CI 0.32–0.96), and neonatal hypoglycemia requiring hospital care (OR 0.09, 95% CI 0.01–0.57). Each 5% increase in overnight TIRp decreased the odds of gestational hypertension (OR 0.71, 95% CI 0.52–0.98) and neonatal hypoglycemia requiring hospital care (OR 0.15, 95% CI 0.03–0.79). Each 5% increase in overall time-above-range (TARp) increased the odds of birthweight >4.5 kg (OR 1.76, 95% CI 1.05–2.96), respiratory distress (OR 1.55, 95% CI 1.02–2.37), and neonatal hypoglycemia requiring hospital care (OR 5.10, 95% CI 1.14–22.78). Each 5% increase in TARp overnight increased the odds of hospital care for neonatal hypoglycemia (OR 2.55, 95% CI 1.15–5.66). Each 0.28 mmol/L increase in mean glucose and 0.5% increase in GMI were associated with increased respiratory distress (OR 1.54, 95% CI 1.07–2.23 and OR 6.15, 95% CI 1.33–28.40). Every 0.28 mmol/L increase in glycemic variability (SD) was associated with gestational hypertension (OR 1.69, 95% CI 1.02–2.80) and birthweight >4.5 kg (OR 2.31, 95% CI 1.20–4.43). Several combinations of CGM metrics (TIRp[-night], TARp[-night], SD, mean glucose) improved discriminative performance for pregnancy outcomes. GMI and HbA1c values were discordant.
Conclusions:
Specific combinations of CGM metrics, including overnight TIRp/TARp, may be informative for predicting pregnancy outcomes. GMI and HbA1c should not be considered interchangeable for glycemic control during pregnancy.