Closed-Loop Insulin Delivery in Type 1 Diabetes in Pregnancy: The CIRCUIT Randomized Clinical Trial

Donovan, LE; Lemieux, P; Dunlop, AD; Yamamoto, JM; Murphy, HR; Simmons, D; Bell, RC; Chaput, KH; Benham, JL; Ross, GP; Nerenberg, KA; Booth, JE; Perkins, BA; Mohammad, K; Ntanda, HN; King, JA; Tomlinson, G; Feig, DS; CIRCUIT Collaborative Group

doi:10.1001/jama.2025.19578

Gestational diabetes & diabetes in pregnancy

Closed-Loop Insulin Delivery in Type 1 Diabetes in Pregnancy: The CIRCUIT Randomized Clinical Trial

JAMAPublished 23 Dec 2025Randomised controlled trial

Primary result · Time in pregnancy-specific glucose rangeResultMean adjusted difference 12.5 percentage points 95% CI 9.5–15.6

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Authors' conclusion

Pregnant women with type 1 diabetes using a closed-loop system spent significantly more time in the pregnancy-specific glucose range than those receiving standard care. These findings support the use of this closed-loop system in pregnant women with type 1 diabetes.

Study context

Population: Pregnant women with T1D enrolled before 14 weeks' gestation, 14 centres in Canada and Australia; mean age 31.7 (SD 5.2) years, early pregnancy HbA1c 7.4% (SD 1.0%)88 in primary analysis
Participants: 91 women

Comparison: Closed-loop therapy vs standard care
Closed-loopn = 46
Standard caren = 45reference
Primary endpoint: Percentage of time in pregnancy-specific glucose range (63-140 mg/dL), by CGM
Follow-up: 16 to 34 weeks' gestation

Methodological detailsopen-label, multicentre, Follow-up until 6 weeks postpartum, Enrollment June 2021 to July 2024; follow-up completed March 2025

Open-label
Multicentre
Follow-up until 6 weeks postpartum
Enrollment June 2021 to July 2024; follow-up completed March 2025

Primary result

Time in pregnancy-specific glucose range

Mean adjusted difference

12.5 percentage points

95% CI 9.5–15.6

P < 0.001

By group

Closed-loop65.4%mean

Standard care50.3%mean

Closed-loopvs Standard care

mean adjusted difference 12.5 percentage points (95% CI 9.5–15.6); P < 0.001

As reported in the abstract

Safety

Events

Outcome	Closed-loop	Standard care
Severe hypoglycemiaEpisodes	1	— not stated in the abstract
DKAEpisodes	2	1

— not stated in the abstract

Original publication

Closed-Loop Insulin Delivery in Type 1 Diabetes in Pregnancy: The CIRCUIT Randomized Clinical Trial. JAMA. Published 23 December 2025. doi:10.1001/jama.2025.19578

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