Adding NPH Insulin to Closed-Loop Pump Systems in Pregnancy
NPH insulin should not be added to closed-loop pump systems in pregnancy; these systems are designed exclusively for rapid-acting insulin analogs, and mixing insulin types in pumps is not recommended and potentially unsafe. 1
Why NPH Cannot Be Used in Insulin Pumps
Insulin pumps require rapid-acting insulin analogs only (such as lispro, aspart, or glulisine), as the stability and pharmacokinetics of these insulins in pump reservoirs and tubing have been confirmed 1
Use of insulin mixtures in pumps has not been evaluated and is explicitly not recommended by diabetes care guidelines 1
NPH insulin is an intermediate-acting suspension that would precipitate in pump tubing and catheters, causing catheter occlusion and unpredictable insulin delivery
Current Status of Closed-Loop Systems in Pregnancy
None of the FDA-approved automated insulin delivery (AID) systems have algorithms designed to achieve pregnancy-specific glucose targets (fasting 70-95 mg/dL, 1-hour postprandial 110-140 mg/dL, 2-hour postprandial 100-120 mg/dL) 1, 2
Any use of hybrid closed-loop systems during pregnancy is considered off-label and requires expert guidance with "assisted" techniques to achieve tighter glycemic control 1, 3
Predictive low-glucose suspend (PLGS) technology may be better suited for pregnancy than full hybrid closed-loop, as the predictive low-glucose threshold aligns with pregnancy targets and allows more aggressive prandial dosing 1
Appropriate Insulin Management Options in Pregnancy
If Continuing Pump Therapy:
Use rapid-acting insulin analogs exclusively in the pump with manual adjustments to basal rates and bolus doses to achieve pregnancy targets 1
Consider alternating between sensor-augmented pump mode and hybrid closed-loop mode at different times of day as needed to meet pregnancy-specific goals 1
Frequent insulin dose titration is essential due to changing insulin requirements throughout pregnancy (insulin needs typically double or triple by the third trimester) 1, 2
If NPH Insulin Is Clinically Indicated:
NPH must be administered as a separate subcutaneous injection, not through the pump system 2
NPH is safe in pregnancy as it does not cross the placenta, making it an appropriate basal insulin option when given by injection 2
This would require a hybrid approach: pump-delivered rapid-acting insulin for boluses and basal adjustments, plus separate NPH injections for additional basal coverage
Alternative Approach - Multiple Daily Injections:
Either multiple daily injections or insulin pump technology can be used effectively in pregnancy with type 1 diabetes, and neither has been shown superior 1, 2
If NPH is preferred for basal coverage, transition from closed-loop pump to a basal-bolus injection regimen using NPH for basal insulin and rapid-acting analogs for mealtime coverage 2
Critical Safety Considerations
Risk of diabetic ketoacidosis is heightened in pregnancy, particularly with type 1 diabetes, and can occur even at moderately elevated glucose levels (>11 mmol/L or 200 mg/dL) 1
Undetected interruptions in pump insulin delivery can lead to ketosis more rapidly during pregnancy, which is of particular concern 1
Hypoglycemia risk increases in the first trimester due to enhanced insulin sensitivity and altered counter-regulatory responses 1, 2
Education about hypoglycemia prevention, recognition, and treatment is essential for pregnant patients and family members 2
Management During Labor and Delivery
For women using insulin pumps during labor, switching to intravenous insulin infusion is preferable 1
If the pump is retained during labor, a personalized protocol for pump output adjustment is required 1
Insulin requirements drop dramatically immediately after placental delivery, necessitating rapid dose reduction (to 50-80% of pre-pregnancy doses or 50% of end-pregnancy doses) 1, 2
Recommended Team-Based Approach
Referral to a specialized center with interprofessional expertise (maternal-fetal medicine, endocrinology, diabetes educators, dietitians) is strongly recommended for managing diabetes technology in pregnancy 1, 2
Candidates for continuing AID systems in pregnancy should be carefully selected based on glycemic control, hypoglycemia history, comfort with technology, and ability to implement assisted techniques with expert guidance 1