- βClosed-loop users spent 65.4% of time in the healthy pregnancy glucose range vs. only 50.3% for standard care β a 12.5 percentage point improvement
- βThe benefit equals roughly 3 extra hours per day with blood sugar in a safer zone during the critical 16β34 week pregnancy window
- βThe study was conducted across 14 clinical centers in two countries, making the findings broadly applicable to real-world pregnant women with type 1 diabetes
| Journal | JAMA |
| Year | 2025 |
| PMID | 41134589 |
What Was This Study About?
Pregnancy with type 1 diabetes is challenging. High blood sugar during pregnancy can cause serious complications for both mother and baby β affecting up to half of all pregnancies with type 1 diabetes. Researchers wanted to know if a closed-loop insulin delivery system (sometimes called an artificial pancreas) could help keep blood sugar in a safer range during pregnancy.
What Is a Closed-Loop System?
A closed-loop system combines a continuous glucose monitor (CGM) and an insulin pump that communicate with each other automatically. A computer algorithm reads your glucose levels and adjusts insulin delivery in real time β without you having to manually calculate doses as often.
How Was the Study Done?
The CIRCUIT trial enrolled 91 pregnant women with type 1 diabetes at 14 hospitals across Canada and Australia. Women joined the study before 14 weeks of pregnancy. They were randomly assigned to either:
- Closed-loop therapy (46 women)
- Standard care β insulin pump or multiple daily injections, plus a CGM (45 women)
The main goal was to measure how much time each group spent within a pregnancy-safe blood sugar range of 63β140 mg/dL, from weeks 16 to 34 of pregnancy.
What Did They Find?
The results were striking:
- Women using the closed-loop system spent an average of 65.4% of their time in the healthy glucose range
- Women on standard care spent only 50.3% of their time in range
- That's a 12.5 percentage point improvement β a highly significant difference
In practical terms, this means closed-loop users had roughly 3 extra hours per day with blood sugar in a safer zone.
What About Safety?
Both groups experienced some serious events, which is not uncommon in type 1 diabetes pregnancies:
- There was 1 episode of severe low blood sugar (hypoglycemia) in the closed-loop group
- There were 2 episodes of diabetic ketoacidosis (DKA) in the closed-loop group and 1 in the standard care group
Overall, the closed-loop system did not raise serious safety concerns compared to standard care.
Why Does This Matter?
Keeping blood sugar in a healthy range during pregnancy reduces the risk of complications like large babies, premature birth, pre-eclampsia, and neonatal intensive care admission. This study, published in the prestigious journal JAMA in 2025, provides strong evidence that closed-loop technology can make a real difference for pregnant women managing type 1 diabetes.
What Should You Do With This Information?
If you have type 1 diabetes and are pregnant β or planning to become pregnant β talk to your diabetes care team about whether a closed-loop system might be right for you. Technology availability may vary depending on your location and insurance coverage.