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Diabetes Metab Res Rev. 2019 Nov 22:e3248. doi: 10.1002/dmrr.3248. [Epub ahead of print]

Case series of a hybrid closed-loop system used in pregnancies in clinical practice.

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Barbara Davis Center for Diabetes, University of Colorado Anschutz Medical Campus, United States.



Hybrid closed-loop (HCL) therapy is rarely studied in pregnancy. We present 3 cases of women with type 1 diabetes who used the Medtronic 670G HCL system for most or all of gestation.


The Medtronic 670G system has a manual mode (no automated insulin delivery) and an auto mode (AM, HCL therapy). Women in this case series used AM off-label in gestation.


Case 1 started HCL therapy in the 2nd trimester, her sensor glucose time spent <3.9 mmol/L and >10 mmol/L improved thereafter. Case 1 had average sensor glucose (ASG) levels of 6.4 ± 2.4 mmol/L in the 1st trimester, 7.0 ± 2.7 mmol/L in the 2nd trimester before HCL use, 7.1± 2.1 mmol/L in the 2nd trimester after HCL use, and 6.8± 1.9 mmol/L in the 3rd trimester. Case 1 continued AM during operative delivery and post-partum. Cases 2 and 3 used HCL therapy throughout gestation but with inconsistent time in AM. When they increased time in AM their glycemic indices improved. Case 2 had ASG of 9.5±3.4 mmol/L, 8.6± 2.9 mmol/L, and 7.9± 2.5 mmol/L in the 1st through 3rd trimesters, respectively. Case 3 had ASG of 11.1± 4.8 mmol/L and 3.9-10 mmol/L in the 1st and 2nd trimesters, respectively. Case 2 continued HCL therapy post-partum, Case 3 did not.


CareLink® Clinical Software only reports the non-pregnant time in range. Nonetheless, this represents the first report of HCL therapy in pregnancy with a system approved by the Food and Drug Administration in non-pregnant populations.


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