Table 7.

Screening for and diagnosis of GDM^a,b

One-step strategy

Perform a 75-g OGTT, with plasma glucose measurement when patient is fasting and at 1 and 2 h, at 24 to 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 to 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),c 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 2d of the following 4 plasma glucose levels (measured fasting and at 1, 2, and 3 h during OGTT) are met or exceeded (Carpenter–Coustan criteria [243]):

• 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)

^aGDM, gestational diabetes mellitus; GLT, glucose load test; OGTT, oral glucose tolerance test.

^bAdapted from the ADA (2).

^cThe screening threshold is set by local consensus.

^dAmerican College of Obstetricians and Gynecologists notes that one elevated value can be used for diagnosis (250).