managing diabetes in pregnancy: how closed-loop insulin systems are improving outcomes
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pregnant women with type 1 diabetes have narrower blood-sugar targets they need to achieve to reduce the risk of adverse pregnancy outcomes.
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pregnancy can play havoc with blood-sugar levels, especially in women with type 1 diabetes.
closed-loop insulin systems—algorithm-controlled insulin pumps that mimic the pancreas— have already revolutionized blood-sugar management for people with type 1 diabetes who aren’t pregnant. researchers are now asking whether this technology can offer the same benefits to pregnant women.
just 0.3 per cent of pregnant women in canada have type 1 diabetes, but nearly half develop high-blood-sugar-related issues such as high blood pressure and pre-term birth. the closed-loop insulin system—also known as an automated insulin delivery (aid) system—includes a continuous glucose monitor (cgm) worn on the skin, an insulin pump placed wherever insulin would normally be injected, and an algorithm that links the two by continually monitoring blood-glucose levels and adjusting insulin delivery.
the system has been very successful at improving blood-sugar levels in people with type 1 diabetes who aren’t pregnant, but there’s been limited research on pregnant women until now.
benefits of closed-loop insulin systems in pregnancy
the circuit randomized clinical trial, conducted across 14 clinical centres in canada and australia, and recently published in the journal of the american medical association (jama), assessed the effectiveness of the aid system for pregnant women with type 1 diabetes. the participants were monitored from 16 to 34 weeks gestation for their time spent in the pregnancy-specific glucose range.
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the study found that closed-loop insulin delivery significantly improved blood-sugar levels compared with standard care, in which participants continued their existing insulin delivery prior to the study. this contributes to the body of research supporting the use of this closed-loop system in the care of pregnant women with type 1 diabetes.
the women who were chosen at random to use the closed-loop system in the circuit trial spent approximately three extra hours a day—12.5 per cent more time—in their target blood-sugar range, compared with those receiving standard care.
it’s known from previous studies that an increase of as little as 72 minutes a day—five per cent of daily time—within the pregnancy-specific glucose range is associated with improved pregnancy outcomes and neonatal health, says endocrinologist dr. lois donovan, clinical professor of medicine and obstetrics and gynecology at the university of calgary’s cumming school of medicine and co-principal investigator of the circuit study.
additionally, using the aid system relieved stress, provided stronger glycemic control and improved sleep. many patients with type 1 diabetes often worry about their blood sugar levels during the night, but with the insulin pump continually making adjustments, they not only achieve better glucose levels but better sleep.
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the evolution of closed-loop insulin systems for diabetes management
the closed-loop system was initially created to help those living with type 1 diabetes make therapy decisions and deliver insulin to their bodies as needed.
before cgms and insulin pumps, patients used the self-monitoring of blood glucose (smbg) test—pricking their fingertips for a drop of blood, applying it to a test strip and using an electronic metre to get an instant blood sugar reading—about four to 10 times a day to check glucose levels and make manual adjustments to their insulin dose.
both the cgm and insulin pump are worn under the skin, covered by an adhesive patch, and are at least three inches away from each other. the two parts communicate wirelessly, allowing glucose readings from the cgm to automatically adjust insulin delivery through the pump.
while this system mimics the pancreas’s role in regulating insulin in response to changing glucose levels, it cannot anticipate meals or precisely calculate carbohydrate intake. as a result, users must manually program meals or deliver a meal-time insulin bolus—a fast-acting dose of insulin taken after meals or in response to a spike in blood glucose.
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for patients with type 1 diabetes, the closed-loop system removes some of the guesswork involved in insulin dosing and alleviates the burden of diabetes management, says donovan. these systems have been extensively studied for patients with type 1 diabetes and are “rapidly becoming the standard of care.”
pregnant women with type 1 diabetes have narrower blood-sugar targets they need to achieve to reduce the risk of adverse pregnancy outcomes such as preeclampsia (high blood pressure that can damage the liver and kidneys), birth defects, neonatal intensive-care admission, and macrosomia, which refers to a baby whose birth weight is larger than normal. hence, monitoring their blood sugar levels is crucial for the health of both the mother and the baby.
“one of the reasons that it was so important for us to test it in pregnancy is that these commercially available systems were not designed to achieve the really tight blood-sugar targets that you need in pregnancy to prevent complications,” says donovan.
one key achievement of the study was programming the closed-loop systems to detect and monitor strict blood-sugar levels. tight blood-glucose targets change from week to week throughout pregnancy, resulting in different insulin needs. for many women, insulin requirements decrease during the first trimester, then increase in the second and third trimesters.
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“by the time they are into their third trimester, they’re often on double and sometimes even triple the amount of insulin that they required outside of pregnancy,” says donovan.
“it’s really important that the system be able to keep up with the rising requirements and increasing insulin resistance that one sees during pregnancy because that’s not what’s seen outside of pregnancy,” says endocrinologist dr. denice feig, professor of medicine at the university of toronto and co-principal investigator of the circuit study. the goal for pregnant women with type 1 diabetes is to be within their target glucose range for 70 per cent of the time, which can be difficult to achieve.
the pregnant women who used the aid system in the study continued to use the system until six weeks post-partum, says donovan.
“and then, once the baby’s delivered, the placenta is delivered, and the person gets very insulin sensitive, there’s an increased risk of severe lows,” says dr. feig. “the system has to be able to adapt to that as well.”
according to gabrielle schmid, a registered dietitian and certified diabetes educator in ottawa, being on a pump is a better way for many patients with type 1 diabetes to manage their levels.
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“and now we’re looking at the algorithms, like what algorithms are actually approved in pregnancy when it comes to hybrid-closed loops,” says schmid. “the algorithms are now showing how you can achieve really tight targets.”
access issues continue to stall the use of closed-loop insulin systems in pregnancy
while the findings are promising for establishing a new standard of care for pregnant women with type 1 diabetes, access to aid systems remains inequitable. although most provinces and territories cover the cost of aid systems, which include a cgm and insulin pump, the different criteria for each insulin pump program may limit access.
for example, in ontario’s assistive devices program, a patient must meet one of these two criteria to be eligible for an insulin pump and cgm device: be unable to recognize or act on hypoglycemia (low blood sugar) or have a severe hypoglycemia history in the past two years, despite optimized insulin therapy. if approved, the patient must continue using the same insulin pump for five years, says feig.
according to diabetes canada, living with type 1 diabetes can have out-of-pocket costs of up to $18,306 a year in certain areas of canada. the aid system consists of the insulin pump and cgm components, which are often bought separately. the insulin pump costs $6,000 to $7,500 and an additional $3,500 a year for supplies, such as insulin cartridges and tubes.
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the cgm device costs $2,000 to $6,000 for the device and an additional $4,800 a year for supplies, including the sensors, which are usually replaced every 14 days. in february 2024, the federal government announced it would establish a fund to increase access to diabetes devices and supplies; details have yet to be announced.
both donovan and feig say they hope this research will encourage women to adopt this technology, as they continue to conduct research in this field. they also hope that there will be more equitable access to the technology across the country.
“there’s evidence to show that more in-target blood sugars help reduce long-term complications of type 1 diabetes,” says donovan. “this was an area where there’s one of the greatest potential benefits, just even in the short-term.”
hanan hammad is a writer and strategist exploring how communication and innovation shape public understanding, particularly around health misinformation. she has worked across public, corporate and research sectors, contributing to organizations including deloitte and the canadian human rights commission. hanan is currently a fellow in journalism & health impact at the dalla lana school of public health.
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