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

Pregnant women with type 1 diabetes have increased risks of adverse maternal and neonatal outcomes, such as congenital anomalies, preeclampsia, preterm birth, and NICU admission. Hyperglycemia is a central modifiable contributor to these complications, but staying within pregnancy-specific glycemic targets is challenging due to narrow glucose range goals, increased insulin resistance later in pregnancy, and greater risk of hypoglycemia early in gestation. Closed-loop insulin systems have improved blood sugar control in nonpregnant populations, but were not designed to meet the unique goals of pregnancy. The Tandem t:slim X2 insulin pump with Control-IQ technology has demonstrated improved glucose control outside of pregnancy, but its safety and effectiveness in pregnant populations remain unknown. This study evaluates the efficacy and safety of Control-IQ use during pregnancy in women with type 1 diabetes. This randomized clinical trial enrolled pregnant women between 2021 and 2024 with type 1 diabetes across 14 specialty clinics in Canada and Australia. Participants met the inclusion criteria if they had type 1 diabetes diagnosed at least one year prior, a confirmed singleton pregnancy, hemoglobin A1c between 6.2% and 10%, and were enrolled before 14 weeks’ gestation. Patients underwent randomization to either closed-loop insulin delivery using the closed-loop technology of interest or to their standard, pre-enrollment insulin therapy. All participants used continuous glucose monitoring. The primary outcome was the percentage of time spent within the pregnancy-specific glucose range between 16 and 35 weeks. Secondary outcomes included measures of glycemic control, hypoglycemia, maternal quality of life, safety events, and exploratory maternal and neonatal outcomes. Statistical analyses used intention-to-treat principles. A total of 94 individuals were enrolled in the trial, of which 88 pregnancies progressed beyond 24 weeks’ gestation and were included in the primary analysis. Baseline characteristics were similar between groups, with a mean maternal age of 31.7 years and a mean baseline hemoglobin A1c of 7.4%. The percentage of time in the pregnancy-specific glucose range increased from 54.2% to 65.4% in the closed-loop group compared with 47.8% to 50.3% in the standard care group. This corresponds to an adjusted between-group difference of 12.5 percentage points (95% CI, 9.5-15.6; P <0.001). Closed-loop therapy was associated with less time spent in hyperglycemia and hypoglycemia, lower mean glucose levels, reduced glycemic variability, and lower hemoglobin A1c at 24 and 34 weeks’ gestation. Rates of severe hypoglycemia and diabetic ketoacidosis were low and similar between groups, and overall maternal and neonatal outcomes were comparable—though rates of neonatal hyperbilirubinemia and neonatal intensive care admissions were higher in the closed-loop group. The findings support the efficacy and safety of the Control-IQ closed-loop insulin delivery system for glycemic control during pregnancy, resulting in an additional 3 hours per day spent within the target glucose range compared with standard care. This improvement was accompanied by reductions in hyperglycemia, hypoglycemia, mean glucose levels, and glycemic variability, and was consistent across baseline glycemic control levels and insulin delivery methods. These results align with prior studies of closed-loop therapy in pregnancy, although effectiveness has varied across systems. Strengths include a multicenter randomized design and broad applicability, while limitations include the open-label design and limited power to detect differences in pregnancy and neonatal outcomes. Overall, these findings support the use of closed-loop insulin delivery to improve glycemic control during pregnancy for patients with type 1 diabetes. (Summarized from 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;334:2176–2185. doi: 10.1001/jama.2025.19578)