Closed-loop insulin delivery during pregnancy complicated by type 1 diabetes

Abstract

Objective: This study evaluated closed-loop insulin delivery with a model predictive control (MPC) algorithm during early (12-16 weeks) and late gestation (28-32 weeks) in pregnant women with type 1 diabetes.

Research design and methods: Ten women with type 1 diabetes (age 31 years, diabetes duration 19 years, BMI 24.1 kg/m(2), booking A1C 6.9%) were studied over 24 h during early (14.8 weeks) and late pregnancy (28.0 weeks). A nurse adjusted the basal insulin infusion rate from continuous glucose measurements (CGM), fed into the MPC algorithm every 15 min. Mean glucose and time spent in target (63-140 mg/dL), hyperglycemic (>140 to ≥ 180 mg/dL), and hypoglycemic (<63 to ≤ 50 mg/dL) were calculated using plasma and sensor glucose measurements. Linear mixed-effects models were used to compare glucose control during early and late gestation.

Results: During closed-loop insulin delivery, median (interquartile range) plasma glucose levels were 117 (100.8-154.8) mg/dL in early and 126 (109.8-140.4) mg/dL in late gestation (P = 0.72). The overnight mean (interquartile range) plasma glucose time in target was 84% (50-100%) in early and 100% (94-100%) in late pregnancy (P = 0.09). Overnight mean (interquartile range) time spent hyperglycemic (>140 mg/dL) was 7% (0-40%) in early and 0% (0-6%) in late pregnancy (P = 0.25) and hypoglycemic (<63 mg/dL) was 0% (0-3%) and 0% (0-0%), respectively (P = 0.18). Postprandial glucose control, glucose variability, insulin infusion rates, and CGM sensor accuracy were no different in early or late pregnancy.

Conclusions: MPC algorithm performance was maintained throughout pregnancy, suggesting that overnight closed-loop insulin delivery could be used safely during pregnancy. More work is needed to achieve optimal postprandial glucose control.

Figure 1

Plasma glucose concentrations and insulin infusion rates are shown during early and late gestation. The dark lines represent the median plasma glucose levels and insulin infusion rates during early pregnancy (visit 1, 14.8 weeks) and the lighter lines during late pregnancy (visit 2, 28.0 weeks). On both visits, a standardized dinner (80 g carbohydrate) was eaten at 1800, followed by an overnight fast until breakfast (60 g carbohydrate) at 0700 h the next morning. Prandial insulin boluses were calculated according to the women’s insulin-carbohydrate ratio and capillary fingerstick glucose levels. Basal insulin infusion rates were calculated using CGM sensor glucose values and the MPC algorithm.