Early Screening and Diagnosis of Gestational Diabetes Mellitus

High-Risk Individuals Requiring Early Screening

• The American College of Obstetricians and Gynecologists (ACOG) recommends early glucose testing for individuals with clinical characteristics consistent with high risk for gestational diabetes mellitus (GDM), such as marked obesity, personal history of GDM, glycosuria, strong family history of diabetes, and membership in high-risk ethnic populations 1, 2
• High-risk women should undergo screening as soon as possible after the first prenatal visit 1

Early Screening Protocol

• The same screening methods used at 24-28 weeks can be applied for early screening, and if early screening is negative, high-risk women should be retested at 24-28 weeks 1, 3

Standard GDM Screening Options (24-28 weeks)

• ACOG endorses a two-step approach for GDM screening at 24-28 weeks, which includes a 50g glucose load test (GLT) and a 100g oral glucose tolerance test (OGTT) 3, 4
• The two-step approach has diagnostic thresholds of fasting ≥95 mg/dL, 1h ≥180 mg/dL, 2h ≥155 mg/dL, and 3h ≥140 mg/dL 3, 5, 6
• ACOG also accepts a one-step approach with a 75g OGTT, which has diagnostic thresholds of fasting ≥92 mg/dL, 1h ≥180 mg/dL, and 2h ≥153 mg/dL 2, 3, 4

Diagnostic Criteria for Overt Diabetes in Early Pregnancy

• For diagnosing overt diabetes in early pregnancy, ACOG recommends using criteria such as fasting plasma glucose ≥126 mg/dL, 2-hour plasma glucose ≥200 mg/dL during OGTT, or random plasma glucose ≥200 mg/dL with symptoms of hyperglycemia 2, 5, 6

Clinical Considerations

• The one-step approach identifies more women with GDM (15-20%) compared to the two-step approach (5-6%) 4, 6
• Women diagnosed by the one-step approach have a 3.4-fold higher risk of developing prediabetes and type 2 diabetes later in life 2, 4