What are the ADA diagnostic criteria for gestational diabetes mellitus (GDM)?

Updated: Jul 08, 2020
  • Author: Samuel T Olatunbosun, MD, FACP, FACE; Chief Editor: George T Griffing, MD  more...
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The ADA has recommended the use of either the one- or two-step approach at 24–28 weeks of gestation in pregnant women not previously known to have diabetes. [1, 4] The one-step approach involves performing a 75-g OGTT, with plasma glucose measurement when the patient is fasting and at 1 and 2 hours in this group of gravida at 24-28 weeks' gestation. Optimally, perform the OGTT in the morning after an overnight fast of at least 8 hours. The diagnosis of GDM is made when any of the following is met or exceeded [1, 4] :

  • Fasting: 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)

The two-step approach is a 1-hour (nonfasting) plasma glucose measurement after a 50-g oral glucose load in women at 24-48 weeks' gestation who were not previously diagnosed with diabetes. If the plasma glucose level after 1 hours is ≥130 mg/dL, 135 mg/dL, or 140 mg/dL (7.2 mmol/L, 7.5 mmol/L, or 7.8 mmol/L, respectively), perform a fasting 100-g OGTT.

The diagnosis of GDM is made if at least two of the following four plasma glucose levels (measured during OGTT) are met or exceeded [1]

  • Fasting: 95 mg/dL (5.3 mmol/L)
  • 1 hour: 180 mg/dL (10.0 mmol/L) 
  • 2 hour: 155 mg/dL (8.6 mmol/L) 
  • 3 hour: 140 mg/dL (7.8 mmol/L) 

This two-step approach is favored by the American Congress of Obstetricians and Gynecologists (ACOG) with the recommendation of either 135 mg/dL (7.5 mmol/L) or 140 mg/dL (7.8 mmol/L). [43]

Women with risk factors for type 2 diabetes are to be screened during the first prenatal visit, using standard diagnostic criteria; if positive, patients should receive a diagnosis of overt, not gestational, diabetes mellitus. Women with a history of GDM should have lifelong screening for the development of diabetes or prediabetes at least every 3 years. [1, 4]

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