What type and dose of insulin is recommended for a pregnant woman with diabetes?

Insulin Management in Pregnancy

Insulin is the preferred and mandatory medication for managing diabetes in pregnancy, with human insulin preparations or specific insulin analogs (lispro, aspart, and detemir) being the safest options that do not cross the placenta. 1, 2, 3

Recommended Insulin Types

First-Line Insulin Options

For rapid-acting insulin:

• Insulin lispro and insulin aspart are safe and effective, classified as FDA Category B for pregnancy 4
• These rapid-acting analogs improve postprandial glucose control more effectively than regular human insulin with reduced hypoglycemia risk 5, 6
• Regular human insulin remains an acceptable alternative if diabetes is well-controlled 5

For basal insulin:

• Insulin detemir is the preferred long-acting analog, demonstrating improved fasting glucose control without increased hypoglycemia compared to NPH insulin 5, 3
• NPH insulin is safe and effective if the patient is already well-controlled on this regimen 5
• Insulin glargine can be continued if needed for excellent glycemic control, though data are more limited 5, 4

Avoid these insulins:

• Insulin glulisine - no pregnancy data available 5, 4
• Insulin degludec - not studied in pregnancy 4

Insulin Dosing Strategy

Initial Dosing and Titration Schedule

First trimester (weeks 0-13):

• Expect decreased insulin requirements due to enhanced insulin sensitivity 1, 2
• Increased hypoglycemia risk requires vigilant monitoring 2, 3
• May need to reduce pre-pregnancy doses by 10-20% 2

Second trimester (starting week 16):

• Insulin resistance begins increasing exponentially 1
• Requirements increase approximately 5% per week through week 36 1
• Adjust doses every 2-3 weeks based on glucose monitoring 2, 3

Third trimester:

• Total daily insulin typically doubles to triples compared to pre-pregnancy doses 1, 2
• May require concentrated insulin formulations in type 2 diabetes 1, 2
• Leveling off of requirements near term may indicate placental aging 1
• Rapid reduction in requirements signals placental insufficiency and requires immediate evaluation 2, 3

Delivery Methods

Both delivery strategies are equally acceptable:

• Multiple daily injections (basal-bolus regimen) 1, 2
• Continuous subcutaneous insulin infusion (insulin pump) 1, 2
• Neither method has demonstrated superiority over the other 2

Glucose Targets for Dose Adjustment

Target the following glucose levels:

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

Monitor glucose 4-6 times daily (fasting and postprandial) to guide insulin adjustments 2, 3

Type-Specific Considerations

Type 1 Diabetes

• Higher complexity due to greater hypoglycemia risk and more difficult glycemic control 1, 2
• Altered counterregulatory responses in pregnancy decrease hypoglycemia awareness 1, 2
• DKA occurs at lower glucose thresholds (euglycemic DKA risk) 1, 2
• Prescribe ketone strips and provide DKA education 1
• Continuous glucose monitoring improves outcomes without increasing hypoglycemia 1

Type 2 Diabetes

• Generally easier glycemic control than type 1 diabetes 1, 2
• May require much higher insulin doses, sometimes necessitating concentrated formulations 1, 2
• Lower hypoglycemia risk overall 5

Gestational Diabetes Mellitus

• Insulin indicated when medical nutrition therapy fails to achieve targets 1
• Rapid-acting analogs (lispro, aspart) effectively reduce postprandial hyperglycemia 7, 6
• Less justification for long-acting analogs given lower hypoglycemia risk 5

Critical Postpartum Management

Immediately after placental delivery:

• Insulin resistance drops precipitously 1, 2
• Resume insulin at either 80% of pre-pregnancy doses or 50% of end-of-pregnancy doses 2
• Close monitoring required to prevent severe hypoglycemia 3

Essential Patient Education

Provide comprehensive education on:

• Prevention, recognition, and treatment of hypoglycemia for patient and family members 1, 2, 3
• Consistent carbohydrate intake to match insulin dosing 1, 3
• DKA prevention and detection, especially for type 1 diabetes 1
• Importance of frequent glucose monitoring 2, 3

Common Pitfalls to Avoid

• Failing to anticipate first-trimester hypoglycemia due to enhanced insulin sensitivity 1, 2
• Inadequate dose escalation in second and third trimesters as resistance increases 1, 2
• Missing placental insufficiency indicated by sudden decrease in insulin requirements 2, 3
• Rapid implementation of tight control in patients with retinopathy, which can worsen eye disease 1
• Inadequate postpartum dose reduction, leading to severe hypoglycemia 2, 3
• Using insulin glulisine or degludec, which lack pregnancy safety data 5, 4