Table 2.7

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, 135, or 140 mg/dL (7.2, 7.5, 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 when at least two* of the following four plasma glucose levels (measured fasting and at 1, 2, and 3 h during OGTT) are met or exceeded (Carpenter-Coustan criteria [154]):
  • Fasting: 95 mg/dL (5.3 mmol/L)

  • 1 h: 180 mg/dL (10.0 mmol/L)

  • 2 h: 155 mg/dL (8.6 mmol/L)

  • 3 h: 140 mg/dL (7.8 mmol/L)

  • GDM, gestational diabetes mellitus; GLT, glucose load test; OGTT, oral glucose tolerance test.

  • * American College of Obstetricians and Gynecologists notes that one elevated value can be used for diagnosis (150).