Hybrid Closed-Loop Insulin Therapy for Type 1 Diabetes in Pregnancy
In this expert conversation, Lois E. Donovan, MD, and Denice Feig, MD, MSc, FRCPC, discuss their late-breaking presentation at the 2025 American Diabetes Association (ADA) Scientific Sessions on the CIRCUIT trial—a randomized multicenter study investigating hybrid closed-loop insulin therapy using Control-IQ technology in pregnancy among individuals with type 1 diabetes. They preview key glycemic and safety outcomes from the trial, explain the need for more effective tools to support glucose control during pregnancy, and highlight the importance of developing pregnancy-specific automated insulin delivery algorithms.
Additional Resource:
- Feig DS, Donovan LE. Randomized multicenter trial of hybrid closed loop insulin therapy using Control-IQ technology in type 1 diabetes in pregnancy. Presented at: American Diabetes Association 85th Scientific Sessions; June 20–23, 2025; Chicago, IL. https://professional.diabetes.org/scientific-sessions
TRANSCRIPTION
Lois E. Donovan, MD: Hi, I'm Dr Lois Donovan. I'm an endocrinologist at the University of Calgary, and the presentation I'm giving at the American Diabetes Association is a late breaking abstract on the CIRCUIT trial, which is a randomized multicenter trial of hybrid closed-loop insulin therapy using Control-IQ technology in type 1 diabetes in pregnancy.
Denice Feig, MD, MSc, FRCPC: I am Dr Denice Feig. I am an endocrinologist and Clinician Scientist at the University of Toronto, and I am the co-PI, along with Dr Lois Donovan, of the CIRCUIT trial.
Consultant360: What are the key themes of the presentation?
Dr Donovan: So the key themes of the presentation that we'll be talking about at the ADA are the glycemic results of this trial, as well as some of the key safety metrics. So specifically, we'll be talking about the time spent in pregnancy range on continuous glucose monitoring and how that compares between those that were randomized to use the closed loop during pregnancy versus those that were randomized to continue with their usual care, that being insulin injections or insulin pump as well as ongoing use of continuous glucose monitoring throughout pregnancy. So the continuous glucose monitor that was used in this study was the Dexcom G6, and that was used continuously from enrollment, throughout pregnancy, until the end of the study,
C360: Why do you feel this topic is particularly relevant right now? What was the impetus of this trial?
Dr Donovan: So the reason that we wanted to pursue this is both myself and Denice have worked for many, many years with women with type 1 diabetes who try so hard to manage their blood sugars during pregnancy safely, to prevent complications in their neonates. And this is a really, really challenging thing to do, because, although we don't want the blood sugars to be too high, the flip side is, if all you're worried about is having high blood sugars, then you put these women at risk of having low blood sugars, which can be quite harmful to their own personal health.
And unfortunately, the available tools that we've had up to this point in pregnancy are inadequate. These women have worked really hard over the years to achieve the control they need in pregnancy. And as health care providers, we have worked along with them very hard to help them achieve these targets, but they're almost impossible to achieve with the tools that we have had in the past, and it's no fault of their own engagement and trying how or that of the health care professionals.
So we're looking for tools to help women achieve the blood sugar control that they need to have to have healthy pregnancies and healthy babies. Because unfortunately, when we look at the outcomes of pregnancies of women with type 1 diabetes, about 50% of those pregnancies are complicated by some sort of factor that's related to high maternal blood sugar.
So there's a real need to address that gap, that challenge.
C360: What were the key findings of this trial?
Dr Donovan: We enrolled 94 women, but three miscarried prior to randomization, and they were randomized 1:1, so that half of them received closed loop therapy and the other half standard care with ongoing continuous glucose monitoring.
Our primary outcome was the percent time in pregnancy range. Pregnancy range being much tighter than what we aim to achieve for type 1 diabetes outside of pregnancy. So the range that we're aiming for in pregnancy is 63 to 140 milligrams per deciliter, and we found that those using closed loop had 12.5 percentage points more time in pregnancy specific glucose range compared to those randomized to standard care, and that was significant, highly significant. That equates to approximately 3 more hours per day spent in pregnancy time in range using this closed loop, automated insulin delivery system compared to standard care.
Really important finding. And what's also important is that with this system, it was able to achieve much greater time in range, but not at the expense of time below range. In fact, time below range was less. It was one percentage point less in those using closed loop. So the main point there being that in order to get more time in range, it was not at the expense of more time below range. In fact, was less time below range as well there was less time above range. So those are our glycemic findings.
Other studies have shown that for every 5% improvement in time in pregnancy range, that is associated with improvement in important neonatal outcomes, including a reduction in neonatal hypoglycemia and a reduction in large for gestational age infants and a reduction in neonatal intensive care unit admissions greater than 24 hours.
Now it is important to recognize, though, that a limitation of this study was that this was not large enough to be adequately powered to assess pregnancy outcomes, including neonatal outcomes.
Dr Feig: I do think that once we're able to publish the findings, the remarkable, difference that AID makes. I think it just adds to the literature that AID is so beneficial in type 1 pregnancy.
Dr Donovan: Absolutely. And I'm just going to jump in there and just build on what Denice said, because I completely agree and the context in which she's placed it.
But I would also note that not all automated insulin delivery systems behave the same in pregnancy, and so that's why it was important to look at this system and not assume that the results from other systems can be applied. Since the impact of automated insulin delivery in pregnancy appears to be system specific.
Dr Feig: I agree with Lois, and we're so happy to see that this system worked so well.
C360: What gaps in knowledge or areas for future research around this topic do you want to see pursued?
Dr Feig: That's a good question. Well, I think larger studies that are able to look at pregnancy outcomes would certainly be welcome. And I think the I would like to see the companies make more pregnancy specific algorithms so that we can really do the best thing for our patients who are pregnant.
Dr Donovan: I completely agree with Denice on that. That's what I was going to emphasize as well, that it's great to see how this contributed to improve blood sugar control in the participants. But we always want more. We want better. We want the very best for the people that we manage with type 1 diabetes in pregnancy. And there is need to continue to refine automated insulin delivery algorithms to make them even better and specific for pregnancy.
Pregnancy is a special situation, as we talked about, where blood sugar control is so important and so critical. And women deserve to have developers of these systems focus on making something that works especially well in pregnancy.