Canadian Trial: Closed-Loop Insulin Pumps Safer in Diabetic Pregnancy

Canadian Trial Shows 'Artificial Pancreas' Technology Dramatically Improves Blood Sugar Control During Diabetic Pregnancy

A study from Canada offers some of the most compelling evidence yet that closed-loop insulin delivery systems — sometimes called an "artificial pancreas" — can meaningfully improve outcomes for pregnant women living with Type 1 diabetes. Published in JAMA in 2025, the CIRCUIT trial tracked 91 Canadian and Australian participants across 14 clinical centers, making it one of the most rigorous studies of its kind ever conducted in this high-risk population.

What Is a Closed-Loop Insulin System?

A closed-loop system combines a continuous glucose monitor (CGM) with an insulin pump that automatically adjusts insulin delivery based on real-time blood sugar readings — no manual calculations required. While this technology has shown strong results in non-pregnant adults, pregnancy introduces unique challenges: blood sugar targets are tighter, insulin needs shift constantly, and the stakes for both mother and baby are extremely high.

What the Canadian Researchers Found

Participants were randomly assigned to either closed-loop therapy or standard care (traditional insulin pump or multiple daily injections, both with CGM). The key measurement was how much time patients spent within the pregnancy-specific safe blood sugar range of 114–252 mg/dL... wait — actually 63–140 mg/dL (3.5–7.8 mmol/L), which is considerably tighter than typical non-pregnancy targets.

The results were striking:

• Closed-loop group: 65.4% of time spent in the safe range
• Standard care group: 50.3% of time in the safe range
• Difference: A statistically significant 12.5 percentage points (p < .001)

To put that in perspective, the standard care group was outside their safe blood sugar zone nearly half the time — a situation that puts both mother and baby at serious risk. The closed-loop group reduced that danger window by roughly one-quarter.

Safety Profile

Severe hypoglycemia (dangerously low blood sugar, below roughly 54 mg/dL or 3.0 mmol/L) occurred in just one participant in the closed-loop group. Two participants in the closed-loop group experienced diabetic ketoacidosis (DKA), as did one in the standard care group — a reminder that no technology eliminates all risks.

How This Compares to US Guidelines

The American Diabetes Association (ADA) currently recommends that pregnant women with Type 1 diabetes aim for fasting blood sugars of 70–95 mg/dL and post-meal peaks below 140 mg/dL. The ADA also endorses CGM use during pregnancy but stops short of mandating closed-loop systems, partly due to limited data. This Canadian trial directly addresses that evidence gap.

Why This Matters for US Patients

Approximately 50% of pregnant women with Type 1 diabetes experience serious complications linked to high blood sugar, including preeclampsia, preterm birth, and large-for-gestational-age babies. Despite FDA approval of several hybrid closed-loop systems in the US — including Tandem's Control-IQ and Medtronic's MiniMed 780G — most have not been specifically validated or labeled for use during pregnancy.

This Canadian trial gives US patients and their OB/endocrinology care teams real-world evidence to have an informed conversation about pursuing closed-loop therapy during pregnancy. Women with Type 1 diabetes who are planning a pregnancy or are already pregnant should ask their endocrinologist whether a closed-loop system is appropriate for their situation and whether their insurance covers it — coverage varies significantly across US states and insurance plans.

Original Study: Donovan, Lemieux, Dunlop et al. "Closed-Loop Insulin Delivery in Type 1 Diabetes in Pregnancy: The CIRCUIT Randomized Clinical Trial." JAMA, 2025. DOI: 10.1001/jama.2025.19578 | PMID: 41134589