The 75 gram 2 hour Oral Glucose Tolerance Test
(OGTT)
At 24 to 28 weeks'
The two hour oral glucose tolerance
test is performed after an
overnight fast on all women not previously found to have overt diabetes or
gestational diabetes (GDM) during testing earlier in their current pregnancy.
To be applied to women without known diabetes before pregnancy.
The test should be
done in the morning after an overnight fast of 8 - 14 hours and after at least
3 days of unrestricted diet (>150 grams carbohydrates per day) and unlimited
physical activity.
-
If the mother's fasting blood sugar is very high some
laboratories will cancel the test and report only the fasting blood sugar.
-
If the mother's fasting blood sugar is in an acceptable range
, then she is given 75 grams of glucose load (usually in the form of a
drink).
-
Blood is collected at 1 and 2 hours after glucose load.
-
The mother should remain seated and should not smoke
throughout the test.
Threshold values for diagnosis of GDM
|
|
Glucose concentration threshold*
|
|
|
Glucose
measure |
mmol/l |
mg/dl |
|
FPG |
5.1 |
92 |
1-h plasma glucose |
10.0 |
180 |
2-h plasma glucose |
8.5 |
153 |
*One or more of these values from a 75-g OGTT
must be equaled or exceeded for the diagnosis of GDM.
|
Postpartum glucose testing should be
performed for all women diagnosed with overt diabetes during pregnancy or GDM
Reprinted with
permission of The American Diabetes Association. |