What is the management plan for a pregnancy complicated by Gestational Diabetes Mellitus (GDM)?

Management of Gestational Diabetes Mellitus in Pregnancy

Lifestyle modification with medical nutrition therapy and physical activity is the cornerstone of GDM management and successfully controls glucose levels in 70-85% of women; insulin must be added as first-line pharmacological therapy when lifestyle measures fail to achieve glycemic targets within 1-2 weeks. 1, 2

Glycemic Targets for Management

Self-monitoring of blood glucose should aim for the following specific targets established by the Fifth International Workshop-Conference on Gestational Diabetes Mellitus 1:

• 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)

These targets apply regardless of whether treatment involves lifestyle alone or includes insulin 1, 2.

First-Line Treatment: Lifestyle Interventions

Medical Nutrition Therapy

Work with a registered dietitian familiar with GDM management to develop a nutrition plan that meets these specific requirements 1, 2:

• Minimum 175 g of carbohydrate daily (approximately 35% of a 2,000-calorie diet)
• Minimum 71 g of protein daily
• 28 g of fiber daily
• Emphasize monounsaturated and polyunsaturated fats while limiting saturated fats and avoiding trans fats 1

The calorie intake should promote appropriate gestational weight gain according to 2009 National Academy of Medicine recommendations based on pregestational BMI 1. There is no evidence that calorie needs differ from pregnant women without GDM 1.

Physical Activity

Exercise interventions improve glucose outcomes and reduce the need for insulin 1. Effective regimens include:

• Aerobic exercise, resistance training, or both
• 20-50 minutes per day
• 2-7 days per week at moderate intensity 1

For generally healthy pregnant women, aim for at least 150 minutes of moderate-intensity aerobic activity weekly, spread throughout the week 3.

Second-Line Treatment: Pharmacological Therapy

When to Initiate Medication

Add pharmacological therapy if glycemic targets are not achieved with lifestyle modifications within 1-2 weeks 4. Women with greater initial hyperglycemia may require earlier initiation 1, 3.

Insulin: The Preferred First-Line Agent

Insulin is the preferred and only recommended first-line medication for treating hyperglycemia in GDM because it does not cross the placenta to a measurable extent. 1, 2, 4

Key insulin prescribing principles 4:

• Use a smaller proportion as basal insulin
• Use a greater proportion as prandial insulin to target postprandial excursions
• Titrate frequently as insulin requirements change dramatically throughout pregnancy

Oral Agents: Not Recommended as First-Line

Metformin and glyburide should NOT be used as first-line agents because 1:

• Both cross the placenta to the fetus 1, 2
• Lack long-term safety data for offspring 1
• Metformin results in umbilical cord blood levels as high or higher than maternal levels 1
• Glyburide has been associated with increased neonatal hypoglycemia and macrosomia compared to insulin 2
• Both agents fail to provide adequate glycemic control in 23-28% of women 3

While individual RCTs have shown limited efficacy of these agents in reducing glucose levels, the lack of long-term safety data and placental transfer make them inappropriate as first-line therapy 1.

Monitoring and Surveillance

• Self-monitoring of blood glucose is essential to assess whether glycemic targets are being met 2
• Monitor blood pressure and urinary protein at each prenatal visit due to increased risk of hypertensive disorders 2
• For women requiring medications or with poor glucose control, fetal surveillance should start at 32 weeks of gestation 5
• 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 5

Telehealth as an Effective Care Delivery Model

Telehealth visits for GDM improve outcomes compared with standard in-person care alone, with demonstrated reductions in 1:

• Cesarean delivery
• Premature rupture of membranes
• Pregnancy-induced hypertension or preeclampsia
• Preterm birth
• Neonatal hypoglycemia
• Neonatal asphyxia
• Polyhydramnios
• Macrosomia

Telehealth can be used in combination with in-person visits 1.

Critical Pitfalls to Avoid

Do not prematurely escalate to medications. Remember that 70-85% of women diagnosed with GDM under Carpenter-Coustan criteria can achieve glycemic control with lifestyle modification alone 1, 2. This proportion is anticipated to be even higher with the lower IADPSG diagnostic thresholds 1.

Do not use oral antihyperglycemic agents as first-line therapy. Despite their convenience, they have inferior safety profiles compared to insulin due to placental transfer and lack of long-term offspring safety data 1, 4.

Do not forget postpartum follow-up. Women with GDM have a 50-70% risk of developing type 2 diabetes over 15-25 years and should be screened for persistent diabetes or prediabetes at 6-12 weeks postpartum using nonpregnancy criteria, then every 1-3 years thereafter 1, 4.

Delivery Timing Considerations

• For women controlling glucose with lifestyle modifications alone: deliver at 39/0 to 40/6 weeks of gestation 5
• For women requiring medications for glucose control: deliver at 39/0 to 39/6 weeks of gestation 5

Delivery during the 39th week of gestation may provide the best balance of maternal and fetal outcomes 5.