TOPLINE:

Compared with standard care, a closed-loop insulin delivery system increased the time spent within the pregnancy-specific glucose target range between 16 and 34 weeks 6 days ’ gestation among pregnant women with type 1 diabetes (T1D), while also reducing exposure to both high and low glucose levels, according to the results of the randomized CIRCUIT trial.

METHODOLOGY:

• Closed-loop insulin delivery systems have shown benefits in nonpregnant populations by reducing hyperglycemia, hypoglycemia, and the burden of diabetes care but have undergone limited testing in pregnancy.
• To assess the efficacy of a closed-loop system in pregnancy, researchers conducted a clinical trial at 14 centers in Canada and Australia, enrolling pregnant women with T1D before 14 weeks’ gestation, with follow-up until 6 weeks postpartum.
• They analyzed 88 participants (mean age, 31.7 years; mean A1c level in early pregnancy, 7.4%) who were randomly assigned by 16 weeks’ gestation to closed-loop therapy or standard care. The standard care group continued their pre-randomization insulin delivery method (multiple daily injections or open-loop subcutaneous infusion pump), and all participants used continuous glucose monitoring throughout the study.
• Recommendations to optimize the closed-loop system for pregnancy included continuous use of the lowest target glucose range (112.5-120 mg/dL, sleep/activity mode) and optional selection of a higher range during exercise.
• The primary outcome focused on the percentage of time glucose levels were in the pregnancy-specific range (63-140 mg/dL), measured using continuous glucose monitoring between 16 weeks and 34 weeks 6 days’ gestation.

TAKEAWAY:

• At 34 weeks 6 days’ gestation, the mean percentage of time in the pregnancy-specific glucose range was significantly higher in the closed-loop group than in the standard care group (65.4% vs 50.3%); the adjusted mean glucose level was 10.7 mg/dL lower in the closed-loop group than in the standard care group.
• Compared with standard care, the closed-loop system reduced the time above 140 mg/dL by 11.5 percentage points and reduced the time below 63 mg/dL by 1.0 percentage point.
• Analysis of safety outcomes showed one episode of severe hypoglycemia in each group, along with two episodes of diabetic ketoacidosis in the closed-loop group and one in the standard care group.

IN PRACTICE:

“These findings support the use of this closed-loop system in pregnant women with type 1 diabetes,” the authors wrote.

“Initiation of automated insulin delivery earlier in gestation could approach the potential maximum effects of optimizing time in the glucose range for pregnancy. Continued work is still needed to optimize automated insulin delivery systems for specific use in pregnant individuals with type 1 diabetes and to ensure access to diabetes technologies to improve the health of both pregnant individuals with type 1 diabetes and their infants,” experts wrote in an accompanying editorial.

SOURCE:

The study was led by Lois E. Donovan, MD, University of Calgary in Calgary, Alberta, Canada. It was published online on October 24, 2025, in JAMA.

LIMITATIONS:

The intervention necessitated an open-label design. The trial was not designed to assess pregnancy outcomes. While the primary analysis adjusted for baseline differences in time in range, some residual imbalance may have remained.

DISCLOSURES:

The study received funding from the MSI Foundation and Diabetes Canada End Diabetes 100 award, the University of Calgary Clinical Research Fund, the Buckley Family Trust, and the Mount Sinai Department of Medicine Research Fund. Some authors reported receiving various forms of support including study supplies, speaker honoraria, personal fees for training and presentations, grants, provision of devices for other studies as well as having scientific advisory roles, and other ties with various pharmaceutical companies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.