What is the management of gestational diabetes mellitus (GDM)?

Management of Gestational Diabetes Mellitus

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

Glycemic Targets

• The recommended glycemic targets for GDM management are 2, 1:
  • Fasting glucose <95 mg/dL (5.3 mmol/L)
  • One-hour postprandial glucose <140 mg/dL (7.8 mmol/L)
  • Two-hour postprandial glucose <120 mg/dL (6.7 mmol/L)

First-Line Management: Lifestyle Modifications

Medical Nutrition Therapy (MNT)

• MNT should be individualized and developed with a registered dietitian familiar with GDM management 2, 1
• The food plan should provide adequate calories to promote fetal/neonatal and maternal health, achieve glycemic targets, and support appropriate gestational weight gain 2
• Specific dietary recommendations include 2, 1:
  • Minimum 175g of carbohydrate daily
  • Minimum 71g of protein daily
  • 28g of fiber daily
• The quality and distribution of carbohydrates are important to manage postprandial glucose excursions 2, 3
• Focus should be on complex carbohydrates with lower glycemic index to avoid postprandial hyperglycemia 3, 4

Physical Activity

• Regular physical activity improves insulin sensitivity and helps achieve glycemic control 2, 5
• At least 150 minutes of moderate-intensity aerobic activity weekly during pregnancy is recommended, preferably spread throughout the week 2
• Exercise interventions have shown improvements in glucose outcomes and reductions in insulin requirements 2, 3

Second-Line Management: Pharmacological Therapy

• Medications should be added if lifestyle modifications fail to achieve glycemic targets 2, 5
• Insulin is the preferred medication for treating hyperglycemia in GDM as it does not cross the placenta to a measurable extent 2, 1
• Metformin and glyburide should not be used as first-line agents as both cross the placenta 2, 1
• If insulin is used, dosing should be adjusted based on self-monitoring of blood glucose levels 2, 5

Insulin Considerations

• Various insulin regimens can be used based on the pattern of hyperglycemia 2, 5
• Insulin requirements may level off toward the end of the third trimester 2
• A rapid and significant reduction in insulin requirements may indicate placental insufficiency 2

Oral Agents (Second-Line Options)

• Metformin crosses the placenta, and while short-term safety data are reassuring, long-term safety data for offspring are lacking 2, 6
• Up to 46% of women on metformin may require additional insulin to maintain expected blood glucose levels 4
• Glyburide also crosses the placenta and has been associated with higher rates 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, 5
• Postprandial monitoring is associated with better glycemic control and lower risk of preeclampsia 2
• Women with GDM have increased risk of hypertensive disorders during pregnancy; blood pressure and urinary protein should be monitored at each prenatal visit 1, 5

Delivery Considerations

• For women with diet-controlled GDM, waiting for spontaneous labor is appropriate if there are no other obstetric indications for earlier delivery 5, 4
• For women requiring medication for glucose control, delivery during the 39th week of gestation may provide the best balance of maternal and fetal outcomes 5
• Consider cesarean delivery if estimated fetal weight exceeds 4,500g to reduce risk of shoulder dystocia 5

Postpartum Management

• Glucose testing shortly after delivery can stratify short-term diabetes risk 7
• Women with GDM have increased risk of developing type 2 diabetes; annual glucose testing is recommended 5, 7
• Lifestyle modifications and breastfeeding may reduce the risk of future diabetes and obesity in both mother and child 5, 7

Common Pitfalls and Caveats

• Failing to recognize that most women (70-85%) can manage GDM with lifestyle modification alone, potentially leading to unnecessary medication use 2, 1
• Assuming oral antihyperglycemic agents are equivalent to insulin in safety and efficacy 2, 1
• Inadequate postpartum follow-up for diabetes screening, missing opportunities for early intervention to prevent type 2 diabetes 5, 7
• Insufficient attention to quality and distribution of carbohydrates in the diet, which significantly impacts postprandial glucose levels 2, 3