Time in range and mean glucose cut-off points for reduction of fetal outcomes in pregnant women with type 1 diabetes using automated insulin delivery systems.

Aim: In pregnant women with Type 1 Diabetes (T1D), achieving a lower recommended time in range (TIRp,63-140 mg/dl) could have an impact on fetal outcomes. To determine the TIRp and mean glucose cut-off point associated with better fetal outcomes in pregnant women using automated insulin delivery (AID) systems.

Methods: A prospective cohort of pregnant women with T1D, using AID systems and followed-up in Latin America was analyzed. Optimal TIRp and mean glucose cut-off points for predicting large for gestational age (LGA) were determined using the Liu method. Fetal outcomes were evaluated for the identified cut-off point and the one recommended by guidelines (TIRp > 70 %).

Results: Sixty-two patients were included (mean age 31.9 ± 5.9 years, HbA1c 7.57 %±1.29 %, TIRp 59.8 %±14.6 %). 27.5 % on advanced hybrid closed loop systems (AHCL). LGA (50 vs 17.9 %,p = 0.010) and hyperbilirubinemia (45 % vs 11.8 %,p = 0.016) were more common in patients with TIRp < 59.1 %. Optimal cut-off of TIRp in the second trimester for predicting LGA was < 59.1 % (sensitivity 75 %, specificity 61 %) with an AUC of 0.68(CI 0.48-0.88). Optimal cut-off for mean glucose was 133 mg/dL (sensitivity 69 %, specificity 70 %) with an AUC of 0.70(CI 0.51-0.88) in the same trimester. Better metabolic control during the third trimester was seen in the AHCL users compared to other devices.

Conclusions: TIRp > 59.1 % and mean glucose < 133 mg/dl in the second trimester, is associated with lower fetal outcomes of large for gestational age. One of the strategies that would improve TIRp is the early use of AHCL systems. Further studies are needed before a strong recommendation can be made.