Table 2.6

Screening for and diagnosis of GDM

One-step strategy
Perform a 75-g OGTT, with plasma glucose measurement when patient is fasting and at 1 and 2 h, at 24–28 weeks of gestation in women not previously diagnosed with diabetes.
The OGTT should be performed in the morning after an overnight fast of at least 8 h.
The diagnosis of GDM is made when any of the following plasma glucose values are met or exceeded:
  • • Fasting: 92 mg/dL (5.1 mmol/L)

  • • 1 h: 180 mg/dL (10.0 mmol/L)

  • • 2 h: 153 mg/dL (8.5 mmol/L)

Two-step strategy
Step 1: Perform a 50-g GLT (nonfasting), with plasma glucose measurement at 1 h, at 24–28 weeks of gestation in women not previously diagnosed with diabetes.
If the plasma glucose level measured 1 h after the load 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), proceed to a 100-g OGTT.
Step 2: The 100-g OGTT should be performed when the patient is fasting.
The diagnosis of GDM is made if at least two* of the following four plasma glucose levels (measured fasting and 1 h, 2 h, 3 h during OGTT) are met or exceeded:
Carpenter-Coustan (86)orNDDG (87)
  • • Fasting

95 mg/dL (5.3 mmol/L)105 mg/dL (5.8 mmol/L)
  • • 1 h

180 mg/dL (10.0 mmol/L)190 mg/dL (10.6 mmol/L)
  • • 2 h

155 mg/dL (8.6 mmol/L)165 mg/dL (9.2 mmol/L)
  • • 3 h

140 mg/dL (7.8 mmol/L)145 mg/dL (8.0 mmol/L)
  • NDDG, National Diabetes Data Group. *ACOG notes that one elevated value can be used for diagnosis (82).