Closed-loop insulin delivery during pregnancy in women with type I diabetes

Zoe Stewart, E. Wilinska Malgorzata, Sara Hartnell, Rosemary C. Temple, Gerry Rayman, Katharine P. Stanley, David Simmons, Graham R. Law, Eleanor M. Scott, Roman Hovorka, Helen R. Murphy

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Background: Outside pregnancy, closed-loop (automated) insulin delivery can improve glycemic control, but its efficacy, safety and feasibility in pregnancy have not been studied.
Methods: We performed an open-label, randomized, crossover study comparing overnight closed-loop with sensor-augmented pump therapy, followed by a day-and-night closed-loop continuation phase. 16 participants completed four weeks of closed-loop (intervention) and sensor-augmented pump therapy (control) in random order. During the feasibility phase, 14 participants continued day-and-night closed-loop until delivery. The primary outcome was the proportion of time with overnight glucose level within target range (63-140mg/dL).
Results: The proportion of time with target overnight glucose levels was higher during closed-loop therapy than control (74.7% vs 59.5%; absolute difference (95% CI) 15.2 percentage points (6.1 to 24.2); p=0.002). The overnight mean glucose level was lower during closed-loop (119 vs 133 mg/dL; p=0.009). There were no significant differences between closed-loop and sensor-augmented pump therapy phases in overnight time spent hypoglycemic (1.9% vs 1.3%; p=0.28), insulin doses or adverse event rates. During the continuation phase (up to 14.6 additional weeks including acute antenatal hospitalizations, labor and delivery), the proportion of time spent in target range was 68.7%; mean glucose level was 126mg/dL. No episodes of severe hypoglycemia requiring third-party assistance occurred during either phase.
Conclusions: Overnight closed-loop therapy resulted in better glucose control than sensor-augmented pump therapy in pregnant women with type 1 diabetes. Day-and-night closed-loop maintained glycemic control a high proportion of the time during antenatal hospital admissions, labor and delivery. (National Institute for Health Research, Diabetes UK; number, ISRCTN71510001) 
Original languageEnglish
Pages (from-to)644-654
Number of pages11
JournalNew England Journal of Medicine
Publication statusPublished - 18 Aug 2016

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