NEW YORK (Reuters Health) – In a small study of pregnant women with type 1 diabetes, use of a closed-loop insulin delivery system (also known as the artificial pancreas) achieved “nearly normoglycemia” overnight, both in early and late pregnancy. This suggests that the control algorithm used safely adapted insulin delivery for advancing gestational age.

This study is the first to describe closed-loop insulin delivery in pregnancy, Dr. Helen R. Murphy of the University of Cambridge Metabolic Research Laboratories, Cambridge, UK, noted in an e-mail to Reuters Health.

“The artificial pancreas was able to safely adjust and increase overnight insulin doses in late pregnancy, to maintain near normal blood glucose levels without nocturnal hypoglycaemia. If confirmed in the home setting, this would allow women with diabetes to sleep peacefully overnight without fear of hypoglycaemia,” Dr. Murphy said.

Continuous glucose monitors (CGM) and insulin pumps can be combined to form closed-loop systems with insulin delivery directed by a control algorithm. Studies have shown improved glucose control and reduced hypoglycemia with overnight use of these systems in children with type 1 diabetes.

“Sensing errors have been considered a major obstacle to effective closed-loop systems,” the study team notes in the January 7 online issue of Diabetes Care. This represents a particular challenge in pregnancy. Currently, data are lacking on performance of control algorithms throughout the physiologic changes of pregnancy.

Dr. Murphy and colleagues evaluated the performance of the Freestyle Navigator CGM and model predictive control (MPC) algorithm in 10 pregnant women with type 1 diabetes.

All of the women were admitted to the Wellcome Trust Clinical Research Facility in Cambridge for 24 hours on two occasions: once between 12 and 16 weeks of pregnancy and again between 28 and 32 weeks of pregnancy.

A nurse adjusted the basal insulin infusion rate from CGMs, fed into the MPC algorithm every 15 minutes. Mean glucose and time spent in target (63 to 140 mg/dL), hyperglycemia (> 140 to 180 mg/dL or higher), and hypoglycemic ( < 63 to 50 mg/dL or less) were calculated using plasma and sensor glucose measurements. During closed-loop insulin delivery, the median plasma glucose level was in the target range in both early and late pregnancy (117 and 126 mg/dL, respectively), the investigators found. The overnight mean plasma glucose time in target was 84% in early and 100% in late pregnancy. Time spent hyperglycemic overnight was 7% in early and 0% in late pregnancy. No time overnight was spent hypoglycemic in early or late pregnancy. “Considered in the context of conventional treatment, whereby women with type 1 diabetes spend on average 16.2% overnight (1.3 hours) hypoglycemic during pregnancy and assuming this group of women were representative, it suggests potential safety benefits of closed-loop insulin delivery,” Dr. Murphy and colleagues point out. In their small study, the MPC algorithm was able to safely increase the insulin infusion rates for advancing gestational age, based on the woman’s weight and total daily insulin dose. “The MPC safety and sensor accuracy data from this study pave the way for future research to refine closed-loop insulin delivery in pregnancy,” they conclude. Reference:
Closed-Loop Insulin Delivery During Pregnancy Complicated by Type 1 Diabetes

Diabetes Care, Published online January 7, 2011.