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, targeting fasting glucose <95 mg/dL, 1-hour postprandial <140 mg/dL, and 2-hour postprandial <120 mg/dL; if these targets are not achieved within 1-2 weeks with lifestyle modifications alone, initiate insulin as the first-line pharmacologic agent. 1, 2

Initial Lifestyle Management

Medical Nutrition Therapy is the cornerstone of GDM management and suffices for 70-85% of women. 1, 3

• Refer to a registered dietitian familiar with GDM management within the first week of diagnosis 2
• Mandatory minimum daily requirements:
  • 175 grams of carbohydrate (never reduce below this threshold as it risks fetal growth compromise and maternal ketosis) 3, 2
  • 71 grams of protein 3, 2
  • 28 grams of fiber 3, 2
• Distribute carbohydrates across 3 small-to-moderate meals and 2-4 snacks throughout the day 3
• Include an evening snack to prevent accelerated ketosis overnight 3
• Emphasize monounsaturated and polyunsaturated fats while limiting saturated fats and avoiding trans fats 3, 2
• Avoid hypocaloric diets <1,200 kcal/day, which cause ketonemia 3

Physical Activity provides significant glycemic benefit and should be prescribed to all women without contraindications. 2, 4

• Prescribe at least 150 minutes of moderate-intensity aerobic activity weekly, spread throughout the week 2
• Regular aerobic exercise lowers fasting and postprandial glucose levels 3

Blood Glucose Monitoring

Self-monitoring of blood glucose is essential to achieve metabolic control and guide treatment decisions. 1

• Check fasting glucose daily upon waking 2
• Check postprandial glucose after each main meal (breakfast, lunch, dinner) 2
• Glycemic targets:
  • Fasting: <95 mg/dL (5.3 mmol/L) 1, 2
  • 1-hour postprandial: <140 mg/dL (7.8 mmol/L) 1, 2
  • 2-hour postprandial: <120 mg/dL (6.7 mmol/L) 1, 2
• Monitor for ketonuria with daily urine ketone testing if there is concern about inadequate intake 3

Pharmacologic Management

Insulin is the preferred and recommended first-line pharmacologic agent when lifestyle modifications fail to achieve glycemic targets within 1-2 weeks. 1, 2

• Insulin does not cross the placenta to a measurable extent, making it the safest option 1, 2
• Metformin and glyburide cross the placenta and have inferior outcomes compared to insulin 2
• The Endocrine Society explicitly recommends avoiding metformin and glyburide as first-line therapy 2
• Insulin regimens should be personalized based on individual glycemic profiles, meal patterns, and activity levels 5

A1C Monitoring

A1C should be used as a secondary measure of glycemic control in pregnancy, after self-monitoring of blood glucose. 1

• Target A1C <6% (42 mmol/mol) is optimal if achievable without significant hypoglycemia 1
• A1C may be individualized between <6% to <7% (42-53 mmol/mol) based on hypoglycemia risk 1
• A1C levels fall during normal pregnancy due to increased red blood cell turnover 1
• A1C may not fully capture postprandial hyperglycemia, which drives macrosomia 1
• Monitor A1C monthly during pregnancy given altered red blood cell kinetics 1

Fetal Surveillance and Delivery Planning

For women requiring medications for glucose control, fetal surveillance should begin at 32 weeks of gestation. 4

• Assess for fetal macrosomia (estimated fetal weight >4,000 g) 4
• Discuss risks and benefits of prelabor cesarean delivery if estimated fetal weight >4,500 g 4
• Delivery timing:
  • Women controlling glucose with lifestyle modifications alone: 39/0 to 40/6 weeks of gestation 4
  • Women requiring medications: 39/0 to 39/6 weeks of gestation 4

Postpartum Follow-Up

Test for persistent diabetes or prediabetes at 4-12 weeks postpartum using a 75-g OGTT with non-pregnancy diagnostic criteria. 2

• Women with GDM have a 50-70% risk of developing type 2 diabetes over 15-25 years 2
• Continued lifestyle modifications, breastfeeding, and metformin can reduce this risk 4
• Insulin resistance typically resolves after delivery 4

Critical Pitfalls to Avoid

• Never reduce carbohydrates below 175 g/day as this compromises fetal growth and causes maternal ketosis 3, 2
• Do not delay insulin initiation beyond 1-2 weeks if lifestyle modifications fail to achieve targets 1, 2
• Do not use metformin or glyburide as first-line agents given their inferior safety profiles 2
• Do not rely solely on A1C for glycemic assessment; prioritize self-monitoring of blood glucose 1