Current practice is to screen all pregnant patients for gestational diabetes (GDM), a condition that affects about 10% of pregnancies, regardless of prior history. However, among patients with a normal 1-hour 50-gram glucose screen (GCT) in a prior pregnancy, the risk of being diagnosed with GDM in a subsequent pregnancy is less than 4% (abstract - .docx). The tool below allows providers to target screening among patients with no history of diabetes and a normal 1h-GCT (<140 mg/dL) in the preceding pregnancy to those at increased risk of GDM. Using a risk cutoff of 15%, the tool has a negative predictive value of 97% and a positive predictive value of 29%.
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Using a cutoff of GDM risk > 15%, this tool has a 97% negative predictive value (NPV) and a 29% positive predictive value (PPV). You may elect to not screen for GDM below this cutoff.