Initial Insulin Dosage for Pregnant Women with Diabetes
For pregnant women with diabetes, insulin therapy should begin with a total daily dose of 0.7-1.0 units/kg in the first trimester, with expected increases to 2-3 times the pre-pregnancy requirements by the third trimester due to physiologic insulin resistance.
Physiological Changes Affecting Insulin Requirements in Pregnancy
Pregnancy creates unique changes in insulin sensitivity that must be considered when dosing insulin:
First trimester: Enhanced insulin sensitivity and lower glucose levels
- Higher risk of hypoglycemia, especially in type 1 diabetes 1
- May require lower insulin doses than pre-pregnancy
Second and third trimesters: Progressive insulin resistance
Initial Insulin Dosing Algorithm
For Pre-existing Type 1 Diabetes:
- Initial total daily dose: 0.7-1.0 units/kg/day
- Distribution: 50% basal insulin, 50% bolus insulin (divided between meals)
- Monitoring: Frequent blood glucose monitoring (fasting and 1-hour postprandial)
- Adjustment: Weekly titration based on blood glucose patterns
For Pre-existing Type 2 Diabetes:
- Initial total daily dose: 0.8-1.0 units/kg/day
- Distribution: 50% basal insulin, 50% bolus insulin
- Note: May require much higher doses and potentially concentrated insulin formulations as pregnancy progresses 1
For Gestational Diabetes:
- Start with diet and lifestyle modifications
- If medication needed, begin with lower doses:
- Initial dose: 0.3-0.5 units/kg/day
- Distribution: Often starting with basal insulin at bedtime if fasting hyperglycemia is the primary issue
Glycemic Targets for Insulin Titration
Insulin should be titrated to achieve these strict targets:
- Fasting glucose: 70-95 mg/dL (3.9-5.3 mmol/L)
- One-hour postprandial glucose: 110-140 mg/dL (6.1-7.8 mmol/L)
- Two-hour postprandial glucose: 100-120 mg/dL (5.6-6.7 mmol/L) 1
Insulin Adjustment Throughout Pregnancy
First trimester:
- Monitor closely for hypoglycemia
- May need to reduce pre-pregnancy insulin doses by 10-20%
- Provide education on hypoglycemia prevention and treatment
16-30 weeks:
- Expect significant increases in insulin requirements (5% per week) 1
- More frequent dose adjustments needed
30-36 weeks:
- Insulin requirements continue to increase but at a slower rate
- Total daily dose typically 2-3 times pre-pregnancy requirements
36 weeks to delivery:
- Insulin requirements typically plateau
- Sudden decrease may indicate placental insufficiency 1
Delivery and Postpartum Considerations
- Insulin resistance drops rapidly with delivery of the placenta 1
- Immediate postpartum period: Reduce insulin to 50% of late pregnancy dose or 80% of pre-pregnancy dose 1
- Monitor closely for hypoglycemia, especially with breastfeeding
Important Caveats and Pitfalls
- Hypoglycemia risk: First trimester carries highest risk; provide education and ketone strips to patients with type 1 diabetes 1
- DKA risk: Pregnancy is a ketogenic state; DKA can occur at lower blood glucose levels than in non-pregnant state 1
- Retinopathy: Rapid implementation of tight glycemic control can worsen retinopathy 1
- Insulin delivery method: Both multiple daily injections and insulin pumps are acceptable; neither has been proven superior during pregnancy 1
- Concentrated insulin: Some women with severe insulin resistance may require U-500 insulin, especially those with type 2 diabetes 2
Monitoring Effectiveness
- Self-monitoring of blood glucose (fasting and postprandial)
- A1C target <6% if achievable without significant hypoglycemia 1
- Consider continuous glucose monitoring, especially for type 1 diabetes 1
Remember that insulin requirements will change dramatically throughout pregnancy, requiring frequent assessment and adjustment of dosing to maintain optimal glycemic control and prevent complications.