I am a pregnant woman with diabetes currently taking NovoMix (insulin aspart protamine‑aspart) 18 units twice daily (bid); how should I manage my insulin therapy and what adjustments are recommended during pregnancy?

Management of Insulin Therapy in Pregnancy with Pre-existing Diabetes

You should immediately transition from NovoMix (biphasic insulin aspart 70/30) to a basal-bolus insulin regimen using insulin aspart for prandial coverage and either NPH or insulin detemir for basal insulin, as insulin is the preferred and recommended treatment for managing pre-existing diabetes during pregnancy. 1

Immediate Insulin Regimen Changes

Why Change from NovoMix?

• NovoMix (premixed insulin) is not the optimal regimen for pregnancy because it does not allow the flexible dose adjustments needed to meet rapidly changing insulin requirements throughout gestation. 1, 2
• Pregnancy requires frequent insulin titration as requirements typically double to triple by the third trimester, necessitating independent adjustment of basal and prandial components. 1, 3

Recommended Insulin Types

For rapid-acting (prandial) insulin:

• Insulin aspart is specifically recommended and studied in pregnancy with randomized controlled trial data demonstrating safety. 2, 4
• The FDA label confirms that insulin aspart use during the second trimester has not been associated with major birth defects or adverse maternal/fetal outcomes. 4

For basal insulin:

• NPH insulin or insulin detemir are the preferred long-acting options for basal coverage in pregnancy. 2
• Insulin glargine is acceptable if you were already well-controlled on it pre-pregnancy, though it has less randomized trial data. 2

Initial Dosing Strategy

Calculate your total daily insulin dose as 0.5 units/kg based on current body weight:

• Divide as 50% basal insulin (given as NPH twice daily or detemir once or twice daily)
• 50% prandial insulin (insulin aspart) distributed across three meals 2

Example: If you weigh 70 kg:

• Total daily dose = 35 units
• Basal: 17-18 units (split if using NPH)
• Prandial: 17-18 units total (divide among breakfast, lunch, dinner based on carbohydrate intake)

Glucose Targets for Titration

Monitor blood glucose 4-6 times daily and adjust insulin to achieve: 1, 2

• Fasting/premeal: 70-95 mg/dL (3.9-5.3 mmol/L)
• 1-hour postprandial: 110-140 mg/dL (6.1-7.8 mmol/L)
• 2-hour postprandial: 100-120 mg/dL (5.6-6.7 mmol/L)
• A1C target: <6% (42 mmol/mol) if achievable without significant hypoglycemia; otherwise <7% (53 mmol/mol) 1, 2

Trimester-Specific Insulin Adjustments

First Trimester (Weeks 0-13)

• Expect insulin requirements to DECREASE by approximately 12% due to enhanced insulin sensitivity. 2, 3
• You are at HIGHEST risk for hypoglycemia during this period. 1, 3
• Monitor glucose closely and reduce doses proactively to prevent severe hypoglycemia. 3

Second and Third Trimester (Weeks 14-36)

• Insulin resistance increases dramatically starting around week 16. 1, 3
• Expect insulin requirements to increase approximately 5% per week through week 36, typically resulting in a doubling or tripling of your total daily dose. 1, 2, 3
• Adjust doses every 2-3 weeks based on glucose patterns. 3

Late Third Trimester (Week 36+)

• Insulin requirements may plateau or even decrease slightly. 1
• A rapid, unexpected reduction in insulin needs may indicate placental insufficiency and requires immediate obstetric evaluation. 1, 2, 3

Critical Safety Considerations

Hypoglycemia Prevention

• Comprehensive education on hypoglycemia prevention, recognition, and treatment is essential for you and family members before, during, and after pregnancy. 1, 3
• Altered counterregulatory responses in pregnancy may decrease your awareness of hypoglycemia. 1
• Always have fast-acting glucose available. 3

Diabetic Ketoacidosis (DKA) Risk

• Pregnancy is a ketogenic state, and DKA can occur at lower blood glucose levels than when not pregnant (even <200 mg/dL). 1, 3
• Obtain urine ketone strips and check ketones if blood glucose >200 mg/dL or if you feel unwell. 1
• DKA carries a high risk of stillbirth and requires immediate emergency care. 1

Retinopathy Monitoring

• Rapid implementation of tight glycemic control can worsen diabetic retinopathy. 1
• Obtain dilated eye examination in first trimester and monitor throughout pregnancy. 1

Additional Pregnancy-Specific Recommendations

Low-Dose Aspirin

• Start aspirin 81 mg daily by the end of the first trimester (ideally by 12 weeks) to reduce preeclampsia risk. 1

Postpartum Insulin Management

• Insulin requirements drop precipitously immediately after delivery. 1, 3
• Resume insulin at either 80% of pre-pregnancy doses OR 50% of end-of-pregnancy doses to prevent severe hypoglycemia. 2, 3
• Close glucose monitoring is required for the first 48 hours postpartum. 2

Specialized Care Referral

• Referral to a specialized diabetes and pregnancy center with team-based care is strongly recommended due to the complexity of insulin management in pregnancy. 2, 3
• This team should include maternal-fetal medicine, endocrinology, diabetes education, and nutrition. 1

Common Pitfalls to Avoid

• Do not continue premixed insulin (NovoMix) throughout pregnancy – it lacks the flexibility needed for appropriate dose adjustments. 1, 2
• Do not wait for hyperglycemia to develop before increasing insulin – anticipate the need for increases starting at 16 weeks. 1, 3
• Do not ignore unexplained reductions in insulin requirements late in pregnancy – this may signal placental problems. 1, 2
• Do not use your pre-pregnancy or end-of-pregnancy insulin doses immediately postpartum – this will cause severe hypoglycemia. 2, 3