Personalized AID Use in Pregnant Women with T1D
Ina Geerts, Kaat Beunen, Mart Peeters, 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 and Katrien Benhalima
Who Benefits Most from Advanced Hybrid Closed Loop Therapy in Pregnancy Across Different Subgroups: A Secondary Analysis of the Randomized Controlled CRISTAL Trial.
Diabetes Technology & Therapeutics 2026;28(3):253–263. Epub 2026 Mar 10.
Managing type 1 diabetes (T1D) during pregnancy is one of the most demanding challenges in diabetes care. Achieving tight glycaemic targets is essential to reduce the risk of maternal and neonatal complications, yet most women fall short of these goals. The CRISTAL trial previously showed that the MiniMed™ 780G advanced hybrid closed loop (AHCL) system did not improve overall pregnancy-specific time in range (TIRp) compared to standard insulin therapy, but did improve overnight TIRp and reduce time below range (TBRp). This secondary analysis, conducted by researchers from KU Leuven, Amsterdam UMC, and multiple Belgian and Dutch centres, investigates which subgroups of pregnant women benefit most from AHCL therapy — an important step towards personalised treatment in T1D pregnancy.
This secondary observational analysis of the CRISTAL randomised controlled trial compared glycaemic outcomes — TIRp, overnight TIRp, TBRp, and overnight TBRp — averaged across four antenatal time points (14, 20, 26, and 33 weeks of gestation) between the AHCL and standard of care groups, within subgroups defined by baseline characteristics. Subgroups were defined by baseline HbA1c, prior AHCL use, educational level, planned pregnancy, and preconception consultation, among others. Linear mixed models were used, and available case analysis was performed given the exploratory nature of the subgroup analyses.
Key findings:
- Women with well-controlled diabetes at baseline benefit most: Women with a baseline HbA1c below 7.0% achieved a significantly higher TIRp with AHCL compared to standard care — a mean difference of 5.64%, corresponding to 1 hour and 21 minutes more time in range per day. Overnight TIRp was nearly 12% higher, and TBRp was significantly lower in this subgroup.
- AHCL-naïve women show the largest gains: Women who had not previously used an AHCL system before pregnancy experienced a 6.29% higher TIRp with the MiniMed 780G — equivalent to 1 hour and 30 minutes more per day — and an 11.91% improvement in overnight TIRp. These findings suggest that initiating AHCL therapy early in pregnancy is beneficial even without prior experience using the system.
- Women without higher education showed significant improvement in TIRp: AHCL users without a post-secondary education level achieved a 7.33% higher TIRp compared to standard care, suggesting that automated insulin delivery may help reduce glycaemic disparities related to educational background.
- Overnight glycaemic control improved across a broad range of subgroups: Significantly higher overnight TIRp with AHCL was observed in women with planned pregnancies and in those who had attended a preconception consultation, in addition to the three primary subgroups above.
- The MiniMed 780G requires active engagement: Women with better baseline glycaemic control more frequently used assisted carbohydrate estimation — a technique that compensates for the system's conservative bolus delivery — suggesting that proactive engagement with the device is key to maximising its benefit, particularly as insulin resistance increases in later pregnancy.
- No significant differences were found by diabetes duration, BMI, age, or parity: These factors did not meaningfully differentiate treatment response, supporting a focus on glycaemic control and technology experience as the primary predictors of AHCL benefit in pregnancy.
This secondary analysis provides clinically meaningful guidance for personalising AHCL therapy in T1D pregnancy. Women with good glycaemic control at the start of pregnancy, no prior experience with closed loop systems, and lower educational attainment appear to derive the greatest benefit from the MiniMed 780G. These findings support early initiation of AHCL therapy in pregnancy and highlight the need for pregnancy-specific algorithms that can better adapt to the physiological changes of gestation — particularly the progressive increase in insulin resistance seen from the second trimester onwards.
Concluding, the authors state
"This underscores the importance of personalized recommendations for AHCL use in clinical practice, while awaiting better-performing AHCL algorithms specifically adapted for pregnancy in diabetes."
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