Changes in basal rates and bolus calculator settings in insulin pumps during pregnancy in women with type 1 diabetes

Objective: To explore insulin pump settings in a cohort of pregnant women with type 1 diabetes on insulin pump therapy with a bolus calculator. Methods: Twenty-seven women with type 1 diabetes on insulin pump therapy were included in this study. At 8, 12, 21, 27 and 33 weeks, insulin pump settings and HbA1c were recorded. Results were compared with 96 women with type 1 diabetes on multiple daily injection therapy. Results: Throughout pregnancy, the carbohydrate-to-insulin ratio decreased at all three main meals. The most pronounced decrease was observed at breakfast, where the carbohydrate-to-insulin ratio was reduced, from median 12 (range 4-20) in early pregnancy to 3 (2-10) g carbohydrate per unit insulin in late pregnancy. Basal insulin delivery increased by similar to 50%, i.e. from 0.8 (0.5-2.2) to 1.2 (0.6-2.5) IU/h at 5 a.m. and from 1.0 (0.6-1.5) to 1.3 (0.2-2.3) IU/h at 5 p. m. during pregnancy. HbA1c levels during pregnancy, the occurrence of severe hypoglycemia and pregnancy outcomes were similar in the two groups. Conclusions: In women with type 1 diabetes on insulin pump therapy with a bolus calculator, the carbohydrate-to-insulin ratio declined 4-fold from early to late pregnancy, whereas changes in basal insulin delivery were smaller.