Diagnosis of Gestational Diabetes Mellitus (GDM)

Screening for gestational diabetes mellitus 

1. 50-g oral glucose load, administered between the 24th and 28th weeks, without regard to time of day or time of last meal. Universal blood glucose screening is indicated for patients who are of Hispanic, African, Native American, South or East Asian, Pacific Island, or Indigenous Australian ancestry. Other patients who have no known diabetes in first-degree relatives, are under 25 years of age, have normal weight before pregnancy, and have no history of abnormal glucose metabolism or poor obstetric outcome do not require routine screening.

2. Venous plasma glucose measure 1 hour later.

3. Value of 130 mg/dL (7.2 mmol/L) or above in venous plasma indicates the need for a full diagnostic glucose tolerance test.

 

Diagnosis of gestational diabetes mellitus 

The diagnosis of GDM is based on an OGTT. Diagnostic criteria for the 100-g OGTT are derived from the original work of O’Sullivan and Mahan modified by Carpenter and Coustan. Alternatively, the diagnosis can be made using a 75-g glucose load and the glucose threshold values listed for fasting, 1 h, and 2 h; however, this test is not as well validated as the 100-g OGTT.

Diagnosis of GDM with a 100-g or 75-g glucose load

	mg/dl	mmol/l
100-g glucose load Fasting 1-h 2-h 3-h	95 180 155 140	5.3 10.0 8.6 7.8
75-g glucose load Fasting 1-h 2-h	95 180 155	5.3 10.0 8.6

Two or more of the venous plasma concentrations must be met or exceeded for a positive diagnosis. The test should be done in the morning after an overnight fast of between 8 and 14 h and after at least 3 days of unrestricted diet (>150 g carbohydrate per day) and unlimited physical activity. The subject should remain seated and should not smoke throughout the test.

 

Related Criteria

Criteria for the Diagnosis of Diabetes Mellitus

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