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OB/GYN
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Gestational Diabetes 2-Step Screening
Flowchart
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1-h 50 g, then 3-h 100 g if abnormal.
Decision
Outcome
Decision
24–28 weeks gestation. First screen?
✓
1-hour 50 g oral glucose challenge
Decision
1-hour glucose?
✓
<140 mg/dL → normal
✓
≥140 mg/dL → 3-hour 100 g OGTT
Outcome
No GDM
Decision
3-hour OGTT — ≥2 abnormal Carpenter–Coustan values?
✓
Yes → GDM
✓
No → no GDM
Outcome
Diet + exercise first; insulin (preferred), or metformin/glyburide if uncontrolled
Targets: fasting <95, 1-h postprandial <140 (or 2-h <120).