A 32-year-old woman at 26 weeks gestation undergoes a 75g oral glucose tolerance test (OGTT) for gestational diabetes mellitus (GDM) screening. Results are: fasting 88 mg/dL, 1-hour 165 mg/dL, 2-hour 142 mg/dL. Which diagnostic criteria should be applied, and what is the diagnosis?

• A Using Carpenter-Coustan criteria: two or more values must be elevated; only 1-hour is above threshold → no GDM
• B Using IADPSG 2010 criteria: at least one value must be at or above threshold (fasting ≥92, 1h ≥180, 2h ≥153); all values are below threshold → no GDM ✓
• C Using DIPSI criteria: only 2-hour post 75g load matters; 142 mg/dL exceeds cutoff of 140 mg/dL → GDM
• D Using WHO 1999 criteria: 2-hour value ≥140 mg/dL after 75g OGTT confirms GDM → GDM diagnosed

Explanation

The IADPSG (International Association of Diabetes in Pregnancy Study Groups) 2010 criteria, recommended by WHO 2013 and adopted in many centers, diagnoses GDM if ANY ONE of the following thresholds is met on a 75g OGTT: fasting plasma glucose ≥92 mg/dL (5.1 mmol/L), 1-hour ≥180 mg/dL (10.0 mmol/L), 2-hour ≥153 mg/dL (8.5 mmol/L). In this patient, fasting is 88 (below 92), 1-hour is 165 (below 180), 2-hour is 142 (below 153)—all values are below their respective thresholds. Therefore, GDM is NOT diagnosed by IADPSG criteria. The DIPSI criteria use only the 2-hour post-75g load (cutoff ≥140 mg/dL after non-fasting test), which would diagnose GDM, but IADPSG criteria are more widely used and this question tests discrimination between criteria.

Reference: Williams Obstetrics, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.