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Closed-Loop Insulin Delivery in Type 1 Diabetes in Pregnancy: The CIRCUIT Randomized Clinical Trial
Lois E Donovan1,2,3, Patricia Lemieux4, Amy D Dunlop1
1Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
JAMA
|October 24, 2025
Summary
Pregnant women with type 1 diabetes using a closed-loop insulin system achieved better glucose control. This system significantly increased time spent within the target pregnancy glucose range compared to standard care.
Area of Science:
- Endocrinology
- Maternal-Fetal Medicine
- Diabetes Technology
Background:
- Hyperglycemia poses significant risks during pregnancy for women with type 1 diabetes.
- Closed-loop insulin systems have shown efficacy in glucose management outside of pregnancy.
- Limited data exists on the use and efficacy of closed-loop systems during pregnancy.
Purpose of the Study:
- To evaluate the effectiveness of a closed-loop insulin system in pregnant women with type 1 diabetes.
- To compare glucose control in pregnant women with type 1 diabetes using a closed-loop system versus standard care.
Main Methods:
- An open-label, randomized trial conducted across 14 centers in Canada and Australia.
- Pregnant women with type 1 diabetes were randomized to either closed-loop therapy or standard insulin management with continuous glucose monitoring.
- The primary outcome measured was the percentage of time spent within the pregnancy-specific glucose range (63-140 mg/dL) from 16 to 34 weeks' gestation.
Main Results:
- The closed-loop group spent a mean of 65.4% of time in the target glucose range, compared to 50.3% in the standard care group.
- This represents a significant adjusted difference of 12.5 percentage points (P < .001).
- Adverse events included one episode of severe hypoglycemia and three episodes of diabetic ketoacidosis across both groups.
Conclusions:
- Closed-loop systems significantly improve time spent within the target glycemic range for pregnant women with type 1 diabetes.
- These findings support the use of closed-loop systems as a beneficial management strategy in this population.
- Further research may explore long-term outcomes and safety profiles.
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