Closed-loop system improves time in glycemic range for pregnant women with diabetes

medwireNews: Pregnant women with type 1 diabetes spend significantly more time within the recommended pregnancy-specific glucose range when using a closed-loop insulin delivery system, compared with standard insulin plus continuous glucose monitoring (CGM), research shows.

The CIRCUIT clinical trial included 88 women (mean age 32 years) with type 1 diabetes who were randomly assigned to receive closed-loop therapy with a Tandem t:slim X2 insulin pump plus Control-IQ technology (Tandem Diabetes Care, San Diego, USA; n=44) or standard care (insulin pump or multiple daily insulin injections; n=44). All participants also used CGM throughout the study.

Lois Donovan (University of Calgary, Alberta, Canada) and co-authors report in JAMA that, at baseline, the unadjusted mean time spent in the pregnancy-specific glucose range of 63–140 mg/dL (3.5–6.7 mmol/L) was 54.2% in the closed-loop and 47.8% in the standard care group.

Between 16 weeks’ and 34 weeks 6 days’ gestation, this increased to 65.4% in the closed-loop group and 50.3% in the standard care group. After adjustment for potential confounders, the time spent in the pregnancy-specific glucose range was 12.5 percentage points higher in the closed-loop group than in the standard care group.

Donavan et al say that this “clinically relevant difference” was equivalent to 3 more hours per day spent in the pregnancy-specific glucose range.

In line with this, women given a closed-loop system spent significantly less time than those given standard care with glucose levels below 63 mg/dL (1.3 vs 2.1%) or above 140 mg/dL (33.3 vs 47.6%) and had significantly lower mean glucose (131.3 vs 148.4 mg/dL; 7.3–8.2 mmol/L) and less glycemic variability (29.8 vs 35.1%).

The researchers also found that the adjusted difference in glycated hemoglobin level was a significant 0.49% lower at 24 weeks’ gestation in the closed-loop group than in the standard care group (5.9 vs 6.5%; 41 vs 48 mmol/mol) and a significant 0.43% lower at 34 weeks’ gestation (6.2 vs 6.6%; 44 vs 51 mmol/mol).

Among the maternal and neonatal outcomes, there were fewer cases of preeclampsia in the closed-loop group than in the standard care group (13.6 vs 25.0%) but gestational age at delivery and number of preterm births were similar between groups.

Babies born to mothers in the closed-loop group were more likely to have neonatal hyperbilirubinemia (38.6 vs 22.7%) and require neonatal intensive care unit admissions longer than 24 hours (31.8 vs 27.3%) than those in the standard care group. Conversely, neonatal shoulder dystocia was less common in the closed-loop group than in the standard care group (6.8 vs 15.9%).

During pregnancy, there was one episode of severe hypoglycemia in the closed-loop group and none in the standard care group, and there was one case of diabetic ketoacidosis in each group.

Donavan and co-investigators note that previous trials of closed-loop systems in pregnant women with type 1 diabetes have shown heterogenous results. This “suggests that some glycemic benefits in pregnancy are system specific, possibly due to the system’s glucose target or target range and rapidity in accommodating changes in insulin resistance during pregnancy,” they write.

The authors continue: “The system used in CIRCUIT is responsive to user adjustments of basal rates and correction factors. Thus, setting adjustments were possible contributing factors in this closed-loop system’s response to pregnancy changes in insulin resistance.”

They conclude that their findings “support the use” of the Tandem t:slim X2 insulin pump plus Control-IQ technology closed-loop system in pregnant women with type 1 diabetes.

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JAMA 2025; doi:10.1001/jama.2025.19578