What are the recommended glucose targets for gestational diabetes mellitus (GDM)?

Glucose Targets for Gestational Diabetes Mellitus (GDM)

The recommended glucose targets for gestational diabetes mellitus (GDM) are fasting plasma glucose <95 mg/dL (5.3 mmol/L) and either 1-hour postprandial <140 mg/dL (7.8 mmol/L) or 2-hour postprandial <120 mg/dL (6.7 mmol/L). 1, 2, 3

Target Glucose Values for GDM

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

These targets are based on recommendations from the Fifth International Workshop-Conference on Gestational Diabetes Mellitus and have been consistently endorsed by the American Diabetes Association across multiple guidelines 1.

Monitoring Recommendations

• Both fasting and postprandial monitoring are essential for optimal glucose control in GDM 1, 2
• Postprandial hyperglycemia is a primary driver of macrosomia and other adverse fetal outcomes in GDM 2
• The timing of peak postprandial glucose excursions varies between patients (range 45-120 minutes after meals) 2
• Postprandial measurements should be taken 1-2 hours after beginning the meal 2
• The choice between 1-hour vs. 2-hour postprandial monitoring can be based on clinical context, with evidence suggesting similar outcomes with either approach 4

HbA1c Targets in Pregnancy

• An HbA1c target of <6% (<42 mmol/mol) is optimal if achievable without significant hypoglycemia 1, 3
• HbA1c should be monitored more frequently during pregnancy (e.g., monthly) due to altered red blood cell kinetics 1, 3
• HbA1c should not replace blood glucose monitoring as it may not adequately detect postprandial hyperglycemia 1

Special Considerations for Pre-existing Diabetes in Pregnancy

For women with pre-existing type 1 or type 2 diabetes who become pregnant, stricter targets are recommended 1, 3:

• Premeal, bedtime, and overnight glucose: 60–99 mg/dL (3.3–5.4 mmol/L) 1
• Peak postprandial glucose: 100–129 mg/dL (5.4–7.1 mmol/L) 1, 3
• A1C <6.0% 1

Management Approach

• Lifestyle modification is the first-line treatment for GDM 1, 2
• Medical nutrition therapy should be individualized with guidance from a registered dietitian 1, 3
• Physical activity of moderate intensity is recommended if not contraindicated 5, 6
• If glucose targets cannot be achieved with lifestyle modifications, insulin therapy should be initiated as the first-choice medication 1, 5
• 70-85% of women diagnosed with GDM under Carpenter-Coustan criteria can achieve adequate control with lifestyle modification alone 1, 7

Pitfalls to Avoid

• Avoid relying solely on HbA1c for monitoring due to altered red blood cell turnover during pregnancy 1, 2
• Be cautious about nocturnal hypoglycemia in patients with tight glucose control 2
• Avoid excessive carbohydrate restriction that could lead to ketosis 2
• Do not base clinical decisions solely on maternal glucose values without considering fetal status 7
• Be aware that insulin requirements typically level off toward the end of the third trimester, and a rapid reduction may indicate placental insufficiency 7

Long-term Follow-up

• All women with GDM should be tested for persistent diabetes or prediabetes at 4-12 weeks postpartum using a 75g OGTT 1, 5
• Lifelong screening for diabetes should be performed at least every 2-3 years using standard non-pregnant criteria 1, 5
• Women should be informed about their increased risk of developing type 2 diabetes and cardiovascular disease at follow-up 5, 6