Your doctor should assess your risk for gestational diabetes at your first prenatal visit. If you already have diabetes and you become pregnant, then you do not need to be screened for gestational diabetes.

If you have risk factors for developing gestational diabetes (such as, obesity, family history for type 2 diabetes, or previous history of gestational diabetes), your doctor may recommend that you undergo glucose tolerance testing as soon as possible. If your initial test is negative, you will be retested between 24 and 28 weeks of gestation.

If you are at average risk, your doctor will give you a screening test between 24-28 weeks of gestation.

You may not need to be screened if you are at low risk for gestational diabetes. But, to be low risk, you must meet all of the following criteria:

  • Less than 35 years of age
  • Normal weight before pregnancy
  • Not a member of an ethnic group with a high risk of diabetes (Hispanic American, African American, Native American, Asian American, Indigenous Australian, Pacific Islander)
  • No history of diabetes in parents or siblings
  • No history of abnormal glucose tolerance
  • No glucose in urine
  • No history of poor outcomes of pregnancy

Screening Tests

For the 50 gram glucose screening test, you do not need to fast. You are given a drink that contains 50 grams of glucose. One hour later, your blood sugar level is tested.

Doctors use different screening tests and cutoff values to suspect the diagnosis. Generally, these 1 hour values range from 130 mg/dL (7.2 mmol/L) to 140 mg/dL (7.8 mmol/L). If your blood glucose is abnormally high at 1 hour, you will need to take a 3-hour glucose tolerance test to confirm the diagnosis. This may occur up to 90% of the time.