Closed-Loop Insulin System Improves Glucose Control in Pregnant Women With Type 1 Diabetes: CIRCUIT Trial
Canada: Researchers have reported that a closed-loop insulin delivery system significantly improves glucose control during pregnancy in women with type 1 diabetes, offering a promising strategy to address the high burden of hyperglycemia-related complications in this population.
The findings come from the CIRCUIT randomized clinical trial, published in JAMA by Lois E. Donovan from the Department of Medicine, Cumming School of Medicine, University of Calgary, and colleagues.
Pregnancy in women with type 1 diabetes is associated with considerable clinical challenges, as nearly half experience complications linked to poor glycemic control. While closed-loop insulin systems—often described as “artificial pancreas” technology—have shown clear benefits in non-pregnant individuals, evidence supporting their use during pregnancy has remained limited. The CIRCUIT trial was designed to fill this gap by evaluating whether such systems can safely and effectively improve glucose management in pregnant women.
This open-label, multicenter trial enrolled pregnant women with type 1 diabetes across 14 clinical centers in Canada and Australia. Participants were recruited before 14 weeks of gestation and followed through pregnancy until six weeks postpartum. Enrollment took place between June 2021 and July 2024, with follow-up concluding in March 2025. Women were randomly assigned in a 1:1 ratio to receive either closed-loop insulin therapy or standard insulin treatment, which included insulin pumps or multiple daily injections combined with continuous glucose monitoring.
The primary outcome focused on the percentage of time participants’ glucose levels remained within the pregnancy-specific target range of 63 to 140 mg/dL between 16 and 34 weeks of gestation. Of the 94 women initially enrolled, 91 were randomized and 88 were included in the primary analysis. The mean age of participants was 31.7 years, and the average hemoglobin A1c levels in early pregnancy were 7.4%.
The study led to the following findings:
- Women using the closed-loop insulin delivery system spent a mean of 65.4% of monitored time within the pregnancy-specific target glucose range, compared with 50.3% among those receiving standard insulin therapy with continuous glucose monitoring.
- The closed-loop system was associated with an adjusted mean increase of 12.5 percentage points in time spent within the target glucose range, corresponding to nearly three additional hours per day of optimal glycemic control, and this difference was statistically significant.
- Safety outcomes were generally similar between the two groups, with one episode of severe hypoglycemia reported in the closed-loop group.
- Episodes of diabetic ketoacidosis occurred in both groups, affecting two participants in the closed-loop group and one participant in the standard care group.
The authors noted limitations, including the open-label design and the lack of power to directly evaluate pregnancy or neonatal outcomes. Nevertheless, earlier evidence indicates that even small gains in time within the pregnancy-specific glucose range can translate into better maternal and fetal outcomes, underscoring the clinical relevance of the observed benefit.
Overall, the findings demonstrate that closed-loop insulin delivery significantly improves glycemic control during pregnancy in women with type 1 diabetes, supporting its wider adoption to reduce hyperglycemia-related risks and enhance maternal and neonatal care.
Reference:
Donovan LE, Lemieux P, Dunlop AD, et al. Closed-Loop Insulin Delivery in Type 1 Diabetes in Pregnancy: The CIRCUIT Randomized Clinical Trial. JAMA. 2025;334(24):2176–2185. doi:10.1001/jama.2025.19578
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