What are the guidelines for managing gestational diabetes mellitus (GDM)?

Management of Gestational Diabetes Mellitus

Lifestyle modification with medical nutrition therapy is the cornerstone of GDM management and suffices for 70-85% of women; when pharmacologic therapy is needed, insulin is the only recommended first-line agent because it does not cross the placenta. 1, 2, 3

Glycemic Targets

Achieve the following blood glucose goals through self-monitoring 1, 2, 3:

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

Postprandial monitoring is superior to preprandial monitoring alone, as it correlates with better glycemic control and lower preeclampsia risk. 1

First-Line Management: Lifestyle Modifications

Medical Nutrition Therapy

Work with a registered dietitian familiar with GDM management to develop an individualized food plan with these specific requirements 1, 2, 3:

• Minimum 175 g carbohydrate daily
• Minimum 71 g protein daily
• 28 g fiber daily
• Emphasize monounsaturated and polyunsaturated fats while limiting saturated fats and avoiding trans fats 2, 3

The amount and type of carbohydrate directly impacts postprandial glucose excursions, making carbohydrate distribution throughout the day critical. 1, 4 Calorie intake should promote appropriate gestational weight gain while achieving glycemic targets. 1, 2

Physical Activity

Prescribe at least 150 minutes of moderate-intensity aerobic activity weekly, spread throughout the week, unless contraindicated. 3, 5 Physical activity improves glucose and insulin levels, contributing to better glycemic control. 4

When to Initiate Pharmacologic Therapy

Add medications if lifestyle modifications fail to maintain glucose levels within target ranges during follow-up monitoring. 1, 2, 3 Women with greater initial degrees of hyperglycemia may require earlier pharmacological intervention. 3

Pharmacologic Therapy Algorithm

First-Line: Insulin

Insulin is the only recommended first-line pharmacologic agent for GDM in the United States because it does not cross the placenta to a measurable extent. 1, 2, 3 This represents the standard of care endorsed by the American Diabetes Association and American College of Obstetricians and Gynecologists. 1, 2

Not Recommended as First-Line

Metformin and glyburide should not be used as first-line agents because both cross the placenta to the fetus. 1, 2, 3 Additional concerns include:

• Metformin fails to provide adequate glycemic control in 23% of women with GDM 3
• Glyburide fails in 25-28% of women and is associated with increased neonatal hypoglycemia and macrosomia compared to insulin 2, 3
• All oral agents lack long-term safety data 1

The evidence is unequivocal on this point across multiple high-quality guidelines from 2019-2025, with the most recent 2025 guidelines reinforcing insulin as the sole first-line recommendation. 2, 3

Monitoring During Pregnancy

• Self-monitoring of blood glucose is essential to assess treatment effectiveness 2, 3
• Monitor blood pressure and urinary protein at each prenatal visit, as women with GDM have increased risk of hypertensive disorders 2
• For patients requiring medications or with poor glucose control, initiate fetal surveillance starting at 32 weeks of gestation 6
• Assess for fetal macrosomia (estimated fetal weight >4,000 g) and discuss risks/benefits of prelabor cesarean delivery if estimated fetal weight exceeds 4,500 g 6

Delivery Timing

• Women controlling glucose with lifestyle modifications alone: deliver at 39/0 to 40/6 weeks of gestation 6
• Women requiring medications for glucose control: deliver at 39/0 to 39/6 weeks of gestation 6

Postpartum Management

Insulin resistance typically resolves after delivery, but continued vigilance is critical. 6 All women with GDM must undergo reevaluation of glucose tolerance with a 75g oral glucose tolerance test 4-12 weeks postpartum using WHO criteria. 5 Women with GDM face a 50-70% risk of developing type 2 diabetes over 15-25 years. 7

Common Pitfalls to Avoid

• Failing to recognize that 70-85% of women achieve targets with lifestyle alone, potentially leading to premature medication initiation 2, 3
• Using metformin or glyburide as first-line therapy when insulin is the evidence-based standard 1, 2, 3
• Inadequate blood glucose monitoring frequency, which prevents timely treatment adjustments 3
• Neglecting to screen for hypertensive disorders, which occur at higher rates in women with GDM 2

Telehealth Considerations

Telehealth visits for GDM patients improve outcomes compared with standard in-person care, reducing cesarean delivery rates, neonatal hypoglycemia, and other complications. 2, 3 This represents a viable alternative care delivery model.