What is the recommended insulin titration protocol (basal‑bolus regimen, initial dosing, glucose targets, and adjustment criteria) for a pregnant woman with pre‑existing type 1 or type 2 diabetes or gestational diabetes requiring insulin?

Insulin Titration in Pregnancy

Initial Insulin Regimen and Dosing

For pregnant women with pre-existing type 1, type 2, or gestational diabetes requiring insulin, initiate a basal-bolus regimen at 0.5 units/kg/day based on current body weight, divided as 50% basal insulin and 50% prandial insulin distributed across three meals. 1

Preferred Insulin Types

• Rapid-acting prandial insulin: Use insulin lispro or insulin aspart as first-line agents, as these have been studied in randomized controlled trials and demonstrate safety in pregnancy. 1
• Basal insulin: Use insulin detemir or NPH insulin as preferred long-acting options. 1
• NPH insulin remains acceptable, particularly when cost is a concern. 1
• Insulin glargine can be considered for women already well-controlled on this regimen pre-pregnancy, despite limited randomized trial data. 1

Delivery Method

• Both multiple daily injections and continuous subcutaneous insulin infusion (pump therapy) are equally acceptable, with neither shown to be superior. 1

Glucose Targets for Titration

For Pre-existing Type 1 or Type 2 Diabetes

• Fasting/premeal glucose: 70-95 mg/dL (3.9-5.3 mmol/L) 2, 3
• 1-hour postprandial: 110-140 mg/dL (6.1-7.8 mmol/L) 2, 3
• 2-hour postprandial: 100-120 mg/dL (5.6-6.7 mmol/L) 2, 3, 1
• A1C target: <6% (42 mmol/mol) if achievable without significant hypoglycemia; may relax to <7% (53 mmol/mol) if necessary to prevent hypoglycemia 2, 3

For Gestational Diabetes on Insulin

• Fasting glucose: 70-95 mg/dL (3.9-5.3 mmol/L) 3, 1
• 1-hour postprandial: 110-140 mg/dL (7.8 mmol/L) 2, 3
• 2-hour postprandial: 100-120 mg/dL (6.7 mmol/L) 2, 3

The lower limits (70 mg/dL) apply only to insulin-treated patients to prevent hypoglycemia; they do not apply to diet-controlled type 2 diabetes. 2

Monitoring Requirements

• Perform self-monitoring of blood glucose (SMBG) at least 4 times daily: fasting and 1-hour postprandial after each meal (breakfast, lunch, dinner). 4
• Preprandial testing is also recommended when using insulin pumps or basal-bolus therapy so that premeal rapid-acting insulin dosage can be adjusted. 2
• Monitor A1C monthly during pregnancy due to increased red blood cell turnover that physiologically lowers A1C. 3, 1
• Maintain daily food records to correlate glucose patterns with carbohydrate intake and facilitate insulin adjustments. 4

Insulin Adjustment Algorithm

Adjusting Prandial Insulin

• If 1-hour postprandial glucose consistently exceeds 110-140 mg/dL: Increase the corresponding mealtime rapid-acting insulin dose by 1-2 units or 10-20% of the current dose. 5
• Adjust each meal's insulin independently based on that specific postprandial reading. 5

Adjusting Basal Insulin

• If fasting glucose remains elevated (≥95 mg/dL) despite adequate prandial insulin: Add or increase basal insulin (NPH at bedtime or long-acting analogue). 4, 1
• Increase basal insulin by 1-2 units or 10-20% of the current dose every 2-3 days until fasting targets are achieved. 5

Trimester-Specific Considerations

• First trimester (weeks 10-16): Insulin requirements typically decrease by approximately 12% due to enhanced insulin sensitivity and lower glucose levels; closely monitor for hypoglycemia and reduce doses as needed. 1
• Second and third trimester (weeks 17-36): Insulin resistance increases progressively, requiring 2-3 fold increases in total daily dose; expect insulin requirements to rise approximately 5% per week through week 36. 2, 1
• After 28 weeks gestation, insulin needs rise by approximately 62% from early pregnancy levels. 1

Critical distinction: Women with type 1 diabetes have higher absolute insulin requirements in the first two trimesters but experience a net fall in requirements (3.7% in first trimester), while women with type 2 diabetes need much greater percentage increases per trimester. 6

Critical Safety Considerations

Hypoglycemia Prevention

• Provide comprehensive education on hypoglycemia prevention, recognition, and treatment to patients and family members before initiating insulin. 1
• Early pregnancy presents the highest risk for hypoglycemia, particularly in type 1 diabetes, due to enhanced insulin sensitivity. 3, 1
• If women cannot achieve targets without significant hypoglycemia, use less stringent individualized targets, particularly in those with a history of recurrent hypoglycemia or hypoglycemia unawareness. 2

Warning Sign of Placental Insufficiency

• A rapid reduction in insulin requirements may indicate placental insufficiency and requires immediate obstetric evaluation. 1

Postpartum Insulin Management

• Immediately after delivery, insulin requirements drop precipitously: Resume insulin at either 80% of pre-pregnancy doses or 50% of end-of-pregnancy doses. 2, 1
• For type 1 diabetes, basal slow insulin should never be stopped due to risk of ketoacidosis. 2
• For type 2 diabetes, continue insulin at half-dose while awaiting diabetologist advice. 2
• For gestational diabetes, stop insulin and monitor blood glucose levels before and 2 hours after meals for 48 hours. 2
• Close monitoring is required in the immediate postpartum period to prevent hypoglycemia. 1

Role of Continuous Glucose Monitoring

• CGM can be used as an adjunct to—not a replacement for—SMBG in pregnancy. 4
• CGM identifies nocturnal hyperglycemia missed by SMBG. 4
• For women using CGM: Target sensor glucose range 63-140 mg/dL, time in range goal >70%, time below range <63 mg/dL goal <4%, and time below range <54 mg/dL goal <1%. 3

Specialized Care Recommendation

Due to the complexity of insulin management in pregnancy, referral to a specialized diabetes and pregnancy center offering multidisciplinary team-based care (endocrinologist, maternal-fetal medicine specialist, registered dietitian nutritionist, and diabetes care and education specialist) is strongly recommended for optimal maternal and fetal outcomes. 1