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

Management of Gestational Diabetes Mellitus (GDM)

Lifestyle modification is the cornerstone of GDM management and is sufficient for 70-85% of women, with insulin being the preferred pharmacological therapy when needed to achieve glycemic targets. 1

Diagnosis and Clinical Features

• GDM is characterized by increased risk of large-for-gestational-age birth weight, neonatal complications, and long-term risk of maternal type 2 diabetes and abnormal glucose metabolism in offspring 1
• Risks increase progressively with maternal hyperglycemia, with no clear inflection points 1
• Offspring exposed to untreated GDM have reduced insulin sensitivity, impaired β-cell compensation, and higher likelihood of impaired glucose tolerance in childhood 1

Treatment Goals

The recommended glycemic targets for GDM management are:

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

First-Line Management: Lifestyle Modifications

Medical Nutrition Therapy (MNT)

• MNT should be individualized and developed with a registered dietitian familiar with GDM management 1
• The food plan should provide adequate calories to promote fetal/neonatal and maternal health, achieve glycemic targets, and support appropriate gestational weight gain 1
• Dietary recommendations include:
  • Minimum 175g of carbohydrate daily 1
  • Minimum 71g of protein daily 1
  • 28g of fiber daily 1
  • Focus on type and distribution of carbohydrates to limit postprandial glucose excursions 2
  • Emphasis on monounsaturated and polyunsaturated fats while limiting saturated fats and avoiding trans fats 1

Physical Activity

• Regular physical activity has beneficial effects on glucose and insulin levels 2
• Physical activity contributes to better glycemic control and should be incorporated into the management plan 2, 3

Second-Line Management: Pharmacological Therapy

When lifestyle modifications fail to achieve glycemic targets, pharmacological therapy should be initiated:

Insulin Therapy

• Insulin is the preferred medication for treating hyperglycemia in GDM as it does not cross the placenta to a measurable extent 1
• Insulin administration should be individualized to achieve the glycemic goals 1
• No specific insulin regimen has demonstrated superiority in GDM management 1
• Insulin dosage may need adjustment based on blood glucose monitoring, physical activity changes, and meal plans 4

Oral Antihyperglycemic Agents

• Metformin and glyburide should not be used as first-line agents as both cross the placenta 1
• Metformin used for polycystic ovary syndrome should be discontinued by the end of the first trimester 1
• Glyburide (glibenclamide) has minimal placental transfer (4% ex vivo) but has been associated with increased neonatal hypoglycemia and macrosomia compared to insulin 1
• Metformin may be less effective than insulin, with up to 46% of women requiring additional insulin to maintain expected blood glucose levels 3
• All oral agents lack long-term safety data for offspring 1

Monitoring and Follow-up

During Pregnancy

• Self-monitoring of blood glucose is essential to assess glycemic control 1
• Telehealth visits for GDM patients improve outcomes compared with standard in-person care 1
• Women with GDM have increased risk of hypertensive disorders during pregnancy; blood pressure and urinary protein should be monitored at each prenatal visit 1

Postpartum Care

• All women with GDM should undergo glycemic testing at 6-12 weeks postpartum 5
• Annual glucose and HbA1c testing can detect deteriorating glycemic control 6
• Breastfeeding may reduce obesity in children and is recommended 6, 5

Common Pitfalls and Caveats

• Failure to recognize that 70-85% of women can manage GDM with lifestyle modification alone, potentially leading to unnecessary medication use 1
• Inadequate monitoring of maternal glucose levels when corticosteroids are used to enhance fetal lung maturity, which may require temporary addition or increase of insulin doses 1
• Overlooking the importance of carbohydrate type and distribution throughout the day, not just total amount 2
• Assuming oral antihyperglycemic agents are equivalent to insulin in safety and efficacy 1
• Neglecting postpartum follow-up for diabetes screening, missing opportunities for early intervention to prevent type 2 diabetes 6

Algorithm for GDM Management

1. Initial approach: Start with lifestyle modifications (MNT and physical activity) 1
2. Monitor: Self-monitor blood glucose levels targeting fasting <95 mg/dL and 1-hour postprandial <140 mg/dL or 2-hour postprandial <120 mg/dL 1
3. If targets not achieved: Add insulin therapy (preferred pharmacological option) 1
4. If insulin not feasible: Consider metformin or glyburide with counseling about placental transfer and limited long-term safety data 1
5. Postpartum: Screen for diabetes at 6-12 weeks postpartum and annually thereafter 5