Pregnancy and Gestational Diabetes Screening

All pregnant women should be screened for gestational diabetes during their pregnancy. Screening may be done by taking the woman's medical history and examining certain risk factors, but an oral glucose tolerance test is also recommended.

What Is the Oral Glucose Tolerance Test for Gestational Diabetes?

The oral glucose tolerance test is used to screen for gestational diabetes. Gestational diabetes is a specific type of diabetes that can develop in some women late in pregnancy (usually after the 24th week). Women who develop this complication do not have diabetes before becoming pregnant.

When Is the Oral Glucose Tolerance Test for Gestational Diabetes Performed?

The test is generally given between the 24th and 28th week of pregnancy. If you have had gestational diabetes before, or if your health care provider is concerned about your risk of developing gestational diabetes, the test may be performed before the 13th week of pregnancy.

What Happens During the Oral Glucose Tolerance Test?

The oral glucose tolerance test involves quickly drinking a sweetened liquid (called Glucola), which contains 50g of glucose. The body absorbs this glucose rapidly, causing blood glucose levels to rise within 30 to 60 minutes. A blood sample will be taken from a vein in your arm about 60 minutes after drinking the solution. The blood test measures how the glucose solution was metabolized (processed by the body).

What Do the Oral Glucose Tolerance Test Results Mean?

A blood glucose level of 140mg/dL or higher will identify 80% of women with gestational diabetes. When that cutoff is lowered to 130mg/dL, the identification increases to 90%. If your blood glucose level was greater than 130 mg/dL, your provider will likely recommend you take another diabetes screening test that requires you to fast (not eat anything) before the test. 

During this second test, called the 100-gram oral glucose tolerance test, your blood glucose level will be tested four times during a three-hour period after drinking the sweetened drink (many flavors are available) cola-like drink. If two out of the four blood tests are abnormal, you are considered to have gestational diabetes.