What is the recommended management for a pregnant woman with gestational diabetes?

Management of Gestational Diabetes Mellitus

Begin immediately with medical nutrition therapy and self-monitoring of blood glucose upon diagnosis, and if glycemic targets are not achieved within 1-2 weeks, initiate insulin as the first-line pharmacologic agent. 1

Initial Management Strategy

Lifestyle modification is the cornerstone of GDM management and should be implemented immediately upon diagnosis. 2, 1 The evidence shows that 70-85% of women diagnosed with GDM can achieve glycemic control with lifestyle changes alone, though this proportion varies based on diagnostic criteria used. 2

Medical Nutrition Therapy

Refer to a registered dietitian familiar with GDM management within the first week of diagnosis to develop an individualized nutrition plan. 1 The dietary prescription must include specific macronutrient minimums: 1, 2

• Minimum 175 g carbohydrate daily (never reduce below this threshold as it may compromise fetal growth) 1, 2
• Minimum 71 g protein daily 1, 2
• Minimum 28 g fiber daily 1, 2
• Emphasize monounsaturated and polyunsaturated fats while limiting saturated fats and avoiding trans fats 1

For overweight women, daily caloric intake should be approximately 2,000-2,200 kcal/day based on pre-pregnancy BMI (30-32 kcal/kg of pre-pregnancy body weight, plus an additional 340 kcal/day in the second trimester). 1

Critical pitfall: Carbohydrate restriction below 175 g/day can compromise fetal growth when total energy intake is inadequate. 1 The amount and type of carbohydrate directly impact postprandial glucose excursions, so nutritional counseling should focus on carbohydrate distribution throughout the day. 3

Physical Activity

Prescribe at least 150 minutes of moderate-intensity aerobic activity weekly, spread throughout the week. 1 Physical activity has beneficial effects on glucose and insulin levels and contributes to better glycemic control. 3, 4

Blood Glucose Monitoring

Implement fasting and postprandial self-monitoring of blood glucose immediately upon diagnosis. 2 The specific monitoring schedule includes: 1

• Fasting glucose daily upon waking
• Postprandial glucose after each main meal (breakfast, lunch, dinner)

Glycemic Targets

The American Diabetes Association and American College of Obstetricians and Gynecologists recommend the following targets: 2, 1

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

Postprandial monitoring is associated with better glycemic control and lower risk of preeclampsia compared to preprandial monitoring alone. 2

Pharmacologic Management

When to Initiate Medication

If glycemic targets are not achieved within 1-2 weeks of lifestyle modifications alone, initiate pharmacologic therapy. 1

First-Line Agent: Insulin

Insulin is the preferred and recommended first-line pharmacologic agent because it does not cross the placenta to a measurable extent. 2, 1, 5 This is a critical distinction from oral agents. 2

Insulin can be administered safely using physiologic basal-bolus dosing to achieve tighter glycemic control while reducing hypoglycemia episodes. 6 The approach requires understanding the pharmacodynamics of different insulin preparations in addition to the patient's glycemic profiles, nutritional intake patterns, physical activity, and timing of sleep cycles. 6

Oral Agents: Not First-Line

Metformin and glyburide should NOT be used as first-line agents. 2, 1 The Endocrine Society specifically recommends avoiding these medications as first-line therapy due to their inferior outcomes and safety profiles compared to insulin. 1 Both medications cross the placenta to the fetus, and all oral agents lack long-term safety data. 2

A1C Monitoring

While A1C may be useful, it should be used as a secondary measure of glycemic control in pregnancy, after self-monitoring of blood glucose. 2 This is because: 2

• A1C levels fall during normal pregnancy due to physiological increases in red blood cell turnover
• A1C may not fully capture postprandial hyperglycemia, which drives macrosomia

If A1C is used, target <6% (42 mmol/mol) if achievable without significant hypoglycemia, with individualized targets ranging from <6% to <7% (53 mmol/mol) based on hypoglycemia risk. 2

Postpartum Follow-Up

Test for persistent diabetes or prediabetes at 4-12 weeks postpartum using a 75-g oral glucose tolerance test with non-pregnancy diagnostic criteria. 1, 5 This is critical because women with a history of GDM have a 50-70% risk of developing type 2 diabetes over 15-25 years. 1

Management Algorithm Summary

1. Immediate upon diagnosis: Start medical nutrition therapy (175g carb minimum, 71g protein, 28g fiber) + self-monitoring of blood glucose (fasting and postprandial) + physical activity (150 min/week) 1
2. Within 1 week: Referral to registered dietitian 1
3. At 1-2 weeks: Assess if glycemic targets achieved (fasting <95,1-hr postprandial <140, or 2-hr postprandial <120 mg/dL) 1
4. If targets not met: Initiate insulin therapy 1
5. Throughout pregnancy: Continue glucose monitoring and adjust insulin as needed 2
6. At 4-12 weeks postpartum: 75-g OGTT to screen for persistent diabetes 1, 5