Case Report - Overcoming the limitation of Medtronic 780G insulin pump in pregnant patient with Type 1 Diabetes Mellitus during 3<sup>rd</sup> trimester of pregnancy — ASN Events
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Case Report - Overcoming the limitation of Medtronic 780G insulin pump in pregnant patient with Type 1 Diabetes Mellitus during 3rd trimester of pregnancy (#135)

Richard Yang 1 , Marjy Grealish 1 , David Simmons 1 2
  1. Department of Endocrinology, Campbelltown and Camden Hospitals, SWSLHD, Sydney, NSW, Australia
  2. Western Sydney University, Sydney, NSW, Australia

Background:
Tight glycaemic control in pregnant patients with type 1 diabetes mellitus (T1DM) is essential to minimise hyperglycaemia-related pregnancy complications. Hybrid closed-loop systems (HCLS) have demonstrated efficacy in optimising glycaemic outcomes during pregnancy. The AiDAPT trial, evaluating the CamAPS FX app, and the CIRCUIT trial, assessing Tandem’s Control-IQ system, both showed significant improvements in time in range (TIR) compared with standard care. In contrast, the CRISTAL trial, which evaluated Medtronic’s MiniMed 780G HCLS (“780G”), did not demonstrate an improvement in TIR relative to standard care.

Case:
We present a case demonstrating a strategy to overcome limitations in the “780G”. SH is a 34-year-old G3P0 woman with T1DM diagnosed at age 13y, who presented late to the pregnancy diabetes clinic at 24 weeks gestation. Her HbA1c was 6.5%, pre-pregnancy weight 130 kg (body mass index 51 kg/m2), with no diabetes-related complications, managed with the ”780G” and metformin 1000 mg twice daily. Her initial TIR was 65%, with time below range 1%, predominantly post-prandial hypoglycaemia. During the third trimester, TIR declined to 60% at 26 weeks. Strengthening the insulin:carbohydrate ratios (ICR) improved TIR to 66% at 28 weeks. Further strengthening of ICRs including “fake” carbohydrate entries worsened TIR to 56% at 30 weeks, attributed to hypoglycaemia with rebound hyperglycaemia, and resistant fasting hyperglycaemia (> 5.5 mmol/L). Adjunctive insulin detemir (10 units nocte) was introduced at 30 weeks, leading to improved fasting glucose levels and TIR to 70% at 33 weeks and 84% at induction of pregnancy, 35 weeks, for hypertension. The baby weighed 3.2g (74th centile) with no neonatal hypoglycaemia.

Conclusion:
Many women with T1DM enter pregnancy using the Medtronic 780G insulin pump. However, the system’s algorithm is insufficiently responsive to the increasing insulin requirements seen later in pregnancy. Increasing ICRs can lead to hypoglycaemia risk, cessation of basal insulin and subsequent rebound hyperglycaemia. Using “fake” carbohydrate entries to augment insulin delivery has variable benefit. This case highlights a potentially effective strategy of utilizing adjunctive medium acting insulin to address some of the limitations of the “780G” in achieving glycaemic targets in such patients.