Background: We aimed to explore insulin pump settings in breastfeeding women with type 1 diabetes.

Methods: Thirteen unselected breastfeeding women with type 1 diabetes on insulin pump therapy included consecutively from April 2016 to October 2017. Blinded continuous glucose monitoring (CGM) for six days was applied at one, two and six months after delivery. Recommendations were intake of 210 grams carbohydrate daily while aiming for glucose target range 4.0-10.0 mmol/l and avoiding hypoglycemia. Immediately after delivery a reduction of total insulin dose by 30% of the pre-pregnancy dose was recommended. Insulin pump target glucose was 5.8 mmol/l.

Results: Median diabetes duration was 22 (range 13-36) years. At one, two and six months, 13, 11 and 8 women, respectively, were breastfeeding and spent ≥72% (25%-99%) of time in the glucose target range and ≤3.8% (0-15.5%) of time with CGM <4.0 mmol/l at night-time and over 24 hours. None of the women experienced severe hypoglycemia. HbA1c was 58 (47-72) mmol/mol and 52 (44 - 60) at six months and pre-pregnancy, respectively, p=0.18. At one, two and six months, the insulin pump settings remained almost stable with basal insulin rates (at 03.00, 08.00, 12.00 and 18.00) 14% lower and the carbohydrate-to-insulin ratios 10% higher than the pre-pregnancy settings.

Conclusions: In breastfeeding women with type 1 diabetes who consumed sufficient amounts of carbohydrates and obtained appropriate glycemic control, the basal insulin rates were 14% lower and carbohydrate-to-insulin ratios 10% higher than before pregnancy. These data are useful when recommending insulin pump settings after delivery.