Closed-Loop Therapy Improves Glycemic Control in Pregnant Women with T1D

Use of hybrid closed-loop technology could help pregnant women with type 1 diabetes maintain their target glucose levels, according to a new study.

A multicenter trial presented at the 85th Scientific Sessions of the American Diabetes Association (ADA 2025), results suggest use of an automated insulin delivery system (AID) with Control-IQ Technology was associated with greater time in race for pregnancy and a lower mean adjusted glucose levels than standard care using continuous glucose monitoring (CGM).

“Managing glucose levels during pregnancy with type 1 diabetes is of critical importance for optimal health in both mother and child,” said lead investigator Lois Donovan, MD, clinical professor at the University of Calgary AB Canada in the Cumming School of Medicine, Department of Medicine, Division of Endocrinology and Metabolism, Department of Obstetrics and Gynecology.2

Although much of the attention paid to diabetes management in recent years has revolved around the revelations of the benefits of GLP-1 receptor agonists beyond glycemic control, advances in diabetes technology have contributed to an ongoing transformation of care for people with diabetes. A contributor to this revolution, the Control-IQ system from Tandem Diabetes Care made history in 2019 as the first approval of an interoperable algorithm for AID systems.3

Among the most persistent challenges for endocrinologists is management of glycemic control during pregnancy. Donovan and colleagues launched the current study to further explore the potential safety and efficacy of a hybrid closed-loop approach among pregnant women with type 1 diabetes relative to standard care.1,2

Conducted at 14 sites in Canada and Australia, the multicenter, open-label trial was designed to compare a hybrid closed-loop insulin therapy treatment regimen using the Tandem t:slim X2 pump and the embedded Control-IQ Technology to adjust insulin delivery based on real-time readings from a Dexcom G6 CGM to standard care with the same CGM. The trial enrolled pregnant women with type 1 diabetes and early pregnancy A1C levels of 6.2% to 10%.1

A total of 91 women from 14 sites were included in the study. Per trial protocol, patients were randomized to their respective treatment arm by 16 weeks of gestation, with 45 randomized to standard care and 46 randomized to hybrid closed-loop therapy. The overall study cohort had a mean age of 32 (SD< 5) years, a mean duration of diabetes of 19 (SD, 8) years, and a mean HbA1c at enrollment of 7.4% (SD, 1.0%).1

The primary outcome of interest was time in range for pregnancy from 16 weeks to 34 weeks of gestation, which was defined as 63 to 140 mg/dL. Investigators noted an intention-to-treat analysis was performed using longitudinal linear mixed effects regression adjusting for baseline time in range for pregnancy y, baseline insulin modality, and clinical center.1

For the primary endpoint, results indicated time in range for pregnancy was significantly greater in the hybrid closed-loop (65.4%; SD, 9.5%) compared to with standard care (50.3%; SD, 13.9%), yielding a mean adjusted difference of +12.6 percentage points (95% CI, 9.9 to 15.2; P <.001). Further analysis revealed hybrid closed-loop users also spent 11.4 percentage points less time above range and 1.04 percentage points less time below 63 mg/dL relative to standard care (both P < 0.001).1

Additionally, investigators highlighted the adjusted mean glucose was 11.2 mg/dL lower with hybrid closed-loop therapy relative to standard care (95% CI, 7.2 to 16.2; p < 0.001). Of note, the aforementioned outcomes correlate to an additional 3 hours more time in range for pregnancy per day among the hybrid closed-loop group relative to standard care.1

Analysis of safety outcomes suggest there were no unexpected safety concerns and safety profile was comparable for each treatment arm. Investigators noted 1 case of severe hypoglycemia occurred in the hybrid closed-loop group and 2 cases of diabetic ketoacidosis in each arm.1

“Our results reflect the importance of evolving automated insulin delivery to support those living with type 1 diabetes when they are pregnant or preparing for pregnancy,” Donovan added.2

References:

1. Donovan LE, Lemieux P, Dunlap A, et al. A Randomized Multicenter Trial of Hybrid Closed-Loop Insulin Therapy with Control-IQ Technology in Type 1 Diabetes in Pregnancy. Presented at: 85th American Diabetes Association Scientific Sessions. June 20 – 23, 2025. Chicago, Illinois.

2. American Diabetes Association. Smart Insulin Tech Helps Pregnant Women with Type 1 Diabetes Maintain Target Blood Glucose Levels | American Diabetes Association. Diabetes.org. Published June 20, 2025. Accessed June 21, 2025. https://diabetes.org/newsroom/press-releases/smart-insulin-tech-helps-pregnant-women-type-1-diabetes-maintain-target

3. Tandem Diabetes Care. Tandem Diabetes Care Announces FDA Clearance of the t:slim X2 Insulin Pump with Control-IQ Advanced Hybrid Closed-Loop Technology | Tandem Diabetes Care. investor.tandemdiabetes.com. Published December 13, 2019. Accessed June 21, 2025. https://investor.tandemdiabetes.com/news-releases/news-release-details/tandem-diabetes-care-announces-fda-clearance-tslim-x2-insulin