Issue: March 2011
March 01, 2011
2 min read

Closed-loop insulin delivery shows promise in pregnant women with type 1 diabetes

Murphy HR. Diabetes Care. 2011;34:406-411.

Issue: March 2011
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Emerging data suggest that overnight closed-loop insulin delivery may be used safely during pregnancy in women with type 1 diabetes.

A small study of 10 pregnant women with type 1 diabetes was conducted to evaluate closed-loop insulin delivery with a model predictive control (MPC) algorithm in early and late gestation. The women were studied for 24 hours, once during early pregnancy (mean of 14.8 weeks) and again during later pregnancy (mean of 28 weeks).

The day before the study, each woman had a FreeStyle Navigator sensor (Abbott Diabetes Care) inserted into the upper arm and calibrated. Those women who required multiple daily injections had their basal insulin withdrawn and replaced with rapid-acting insulin aspart (Novo Nordisk). All women were connected to an insulin pump (Deltec Cozmo, Smiths Medical) delivering insulin aspart. Then, a nurse adjusted basal insulin infusion rates from continuous glucose measurements (CGMs) fed into the MPC algorithm every 15 minutes.

According to the results, mean plasma glucose levels were 117 mg/dL in early pregnancy and 126 mg/dL in late pregnancy during closed-loop insulin delivery (P=.72). Overnight, the mean plasma glucose time in target (63 mg/dL-140 mg/dL) was 84% during early pregnancy and 100% in late pregnancy (P=.09). Overnight time spent in the hyperglycemic range (>140 mg/dL) was 7% in early pregnancy and 0% in late pregnancy (P=.25), and overnight time spent in the hypoglycemic range (<63 mg/dL) was 0% in both early and late pregnancy (P=.18).

“Closed-loop insulin delivery was associated with nearly normoglycemia overnight, both in early and late pregnancy, suggesting that the MPC algorithm safely adapts insulin delivery for advancing gestational age,” the researchers wrote.

There was no difference in postprandial glucose control, glucose variability, insulin infusion rates and CGM sensor accuracy in early or late pregnancy.

The next step, according to the researchers, is randomized controlled studies of closed-loop insulin delivery with tighter glycemic targets both in the hospital and in the home settings, as well as a randomized study comparing closed-loop with sensor-augmented pump therapy in this population.

“CGM studies indicate that pregnant women with type 1 diabetes spend an average of 10 hours daily with glucose levels outside the recommended target, even with apparently safe HbA1c levels. Hence, their pregnancy outcomes remain suboptimal, with increased risks both of adverse pregnancy outcome and of perinatal morbidity,” the researchers wrote. “A closed-loop system with physiologically responsive insulin adjustments capable of maintaining near-normal glucose levels could be of great benefit for pregnant women with type 1 diabetes.”

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