What are the management options for Gestational Diabetes Mellitus (GDM)?

Management of Gestational Diabetes Mellitus (GDM)

The management of gestational diabetes mellitus should begin with lifestyle modifications as the cornerstone of treatment, with insulin as the first-line pharmacological therapy when lifestyle modifications alone fail to achieve glycemic targets. 1

Initial Management: Lifestyle Modifications

Medical Nutrition Therapy

• An individualized nutrition plan should be developed with a registered dietitian familiar with GDM management 2, 1
• The nutrition plan should provide:
  • Minimum 175g of carbohydrate daily (35% of a 2,000-calorie diet) 2
  • Minimum 71g of protein daily 2
  • 28g of fiber daily 2
  • Emphasis on monounsaturated and polyunsaturated fats while limiting saturated fats and avoiding trans fats 2
• Carbohydrate type, amount, and distribution should be carefully monitored as they significantly impact postprandial glucose excursions 3

Physical Activity

• Regular exercise improves glucose outcomes and can reduce the need for insulin 2
• Effective exercise regimens include:
  • 20-50 minutes per day
  • 2-7 days per week
  • Moderate intensity
  • Can include aerobic, resistance, or both types of exercise 2

Glycemic Targets

• Fasting glucose: <95 mg/dL (5.3 mmol/L) 2, 1
• One-hour postprandial glucose: <140 mg/dL (7.8 mmol/L) 2, 1
• Two-hour postprandial glucose: <120 mg/dL (6.7 mmol/L) 2, 1

Pharmacological Management

When to Initiate Medication

• Approximately 70-85% of women diagnosed with GDM can achieve glycemic targets with lifestyle modifications alone 2, 1
• Pharmacological therapy should be initiated when glycemic targets are not achieved despite adherence to lifestyle modifications 4
• Women with higher initial degrees of hyperglycemia may require earlier initiation of pharmacological therapy 2

First-Line Medication: Insulin

• Insulin is the first-line pharmacological agent recommended for GDM treatment in the U.S. 2, 1
• Key advantages of insulin:
  • Does not cross the placenta to a measurable extent 1
  • Proven efficacy in improving perinatal outcomes 2

Alternative Medications (Second-Line)

• Metformin:

  • Associated with lower risk of neonatal hypoglycemia and less maternal weight gain than insulin 2
  • Concerns include:
    • Readily crosses the placenta, with cord blood levels as high or higher than maternal levels 2
    • Long-term follow-up studies show potential for higher BMI and increased obesity in offspring 2
    • Up to 46% of women may require additional insulin to maintain glycemic targets 5

• Sulfonylureas (e.g., glyburide):

  • Cross the placenta with cord plasma concentrations approximately 50-70% of maternal levels 2
  • Associated with increased risk of neonatal hypoglycemia and macrosomia compared to insulin 2, 1

Monitoring and Follow-up

• Self-monitoring of blood glucose is essential to assess glycemic control 1
• Regular prenatal visits should include monitoring of blood pressure and urinary protein due to increased risk of hypertensive disorders 1
• For patients requiring medication or with poor glucose control, fetal surveillance is recommended starting at 32 weeks gestation 4

Delivery Considerations

• For women controlling GDM with lifestyle modifications alone: delivery at 39/0 to 40/6 weeks of gestation 4
• For women requiring medications: delivery at 39/0 to 39/6 weeks of gestation 4
• Consider prelabor cesarean delivery if estimated fetal weight exceeds 4,500g 4

Common Pitfalls and Caveats

• Failing to recognize that most women (70-85%) can manage GDM with lifestyle modifications alone, potentially leading to unnecessary medication use 2, 1
• Assuming oral antihyperglycemic agents are equivalent to insulin in safety and efficacy 1
• Neglecting postpartum follow-up for diabetes screening, as women with GDM have increased risk of developing type 2 diabetes 4, 5
• Inadequate monitoring of fetal growth, which is essential to detect macrosomia and plan delivery accordingly 4