This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
This study included pregnant women with type 1 diabetes, who were all using continuous glucose monitoring. A closed-loop system that automatically adjusts insulin delivery in real-time, was compared with standard therapy (a standard pump releasing low levels of insulin, topped up with injections).
In this study, women who used the closed-loop system:
- spent 2.5 more hours per day in the target blood sugar range for pregnant women, compared with those receiving standard therapy
- reported no unexpected safety issues.
The National Institute of Health and Care Excellence (NICE) now recommends closed-loop as an option for all women with type 1 diabetes who are pregnant or planning pregnancy.
For more information on type 1 diabetes in pregnancy, visit the NHS website.
The issue: is closed-loop effective for pregnant women with type 1 diabetes?
People with type 1 diabetes cannot produce enough insulin and, without treatment, would have high blood sugar levels. People with the condition therefore need to take insulin throughout the day.
During pregnancy, control of blood sugar levels is more difficult because of changing hormones and eating patterns, and insulin-resistance. As a result, half of the babies born to women with type 1 diabetes have complications, such as early birth and large birthweight. The target blood sugar range in pregnancy is more stringent than the target at other times.
Standard therapy can mean multiple daily injections and/or a standard insulin pump. Standard pumps deliver insulin throughout the day; people top up with extra doses when eating, or for example during illness, if blood sugar levels are above target. People typically make insulin adjustments 7 – 10 times per day, which is onerous especially during pregnancy. A closed-loop system automatically adjusts insulin levels according to blood sugar levels every 10 minutes. It requires less user input although people still require top up doses when eating.
Closed-loop systems have been shown to improve blood sugar control in adults and children; however, before this study it was unclear whether they are effective in pregnancy. This trial compared closed-loop systems with standard insulin therapy in pregnant women with type 1 diabetes.
What’s new?
This randomised controlled trial included 124 pregnant women with type 1 diabetes from 9 hospitals in England, Scotland and Northern Ireland. Their average age was 31 and most (93%) were white.
Before 16 weeks’ gestation, 63 women received a standard insulin pump and 61 received a closed-loop system. Both groups had continuous glucose monitoring on their phone.
The main outcome was the amount of time the women spent within the blood sugar target range for pregnant women (3.5 to 7.8 mmol/L) until they gave birth.
The study found that the closed-loop group:
- spent more time (68%) within the target range than the standard pump group (56%); this is an extra 2.5 hours per day
- spent less time above range (29%) than the standard pump group (41%).
Among those who started treatment in their first trimester, the closed-loop group spent more time (5%) in the target range than the standard pump group.
There were no unexpected safety problems for women using closed-loop. Similar numbers (6 with closed-loop; 5 with standard pumps) had severely low blood sugar levels (hypoglycaemia) and required help.
Why is this important?
In this study, closed-loop effectively controlled blood sugar levels in pregnant women with type 1 diabetes.
Previous research has linked 5% more time spent within the target blood sugar range with improved pregnancy outcomes, including fewer intensive care admissions. This study did not compare pregnancy outcomes but found the closed-loop group spent 10% more time in the target range. This difference could have health benefits for pregnant women and their babies.
Women using closed-loop had fewer unscheduled clinic visits than those using standard pumps in the study. The researchers say they are therefore unlikely to need more help from clinicians.
What’s next?
The researchers are implementing the closed-loop system across the NHS in collaboration with the NHS England diabetes and maternity programmes, the Diabetes Technology Network, and the charities Juvenile Diabetes Research Foundation, and Diabetes UK.
The research team carried out a related study exploring the views of 19 clinicians on using closed-loop during pregnancy. They noted benefits to health and quality of life (convenience, for example). To get the most benefit from the system, they said women and clinicians need to work together with the technology. All pregnant women with type 1 diabetes could be offered closed-loop, they said.
Further research with the same group of clinicians suggested training and ongoing mentorship for clinicians in the national roll-out of closed-loop to help them support women with the technology would be helpful. Pregnant women and clinicians would benefit from 24-hour manufacturer support, they said. Interviewees were optimistic that, with training, their workloads could be reduced because closed-loop reduced pregnant women’s need for support in managing type 1 diabetes.
You may be interested to read
This is a summary of: Lee T, and others. Automated Insulin Delivery in Women with Pregnancy Complicated by Type 1 Diabetes. New England Journal of Medicine 2023; 389: 1566 – 1578.
A podcast by ReachMED summarising the study’s findings.
Information on type 1 diabetes during pregnancy and closed-loop systems from Diabetes UK.
A study exploring the views of women using closed-loop: Julia L, and others. Listening to women: Experiences of using closed-loop in type 1 diabetes pregnancy. Diabetes Technology & Therapeutics 2023. DOI: 10.1089/dia.2023.0323.
Information on taking part in NIHR research on type 1 diabetes.
Funding: This study was funded by the NIHR Efficacy and Evaluation Mechanism programme.
Conflicts of Interest: Multiple authors have received fees and funding from pharmaceutical companies. Details are available in the original paper.
Disclaimer: Summaries on NIHR Evidence are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that the views expressed are those of the author(s) and reviewer(s) at the time of publication. They do not necessarily reflect the views of the NHS, the NIHR or the Department of Health and Social Care.
