Health Information

Screening for Gestational Diabetes

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 are at high risk of developing gestational diabetes (eg, obesity , family history for type 2 diabetes , 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.

  • If your blood sugar level is less than 130 mg/dL (7.2 mmol/L) at the one-hour mark—The likelihood that you have gestational diabetes is low. You do not require further testing.
  • If your blood sugar level is greater than 130 mg/dL (7.2 mmol/L)—The test is considered positive (abnormal). Your chance of having gestational diabetes is 90%. You will need to take the three-hour oral glucose tolerance test to confirm the diagnosis. Not all women that have an abnormal or positive 50-gram glucose test have gestational diabetes.

Note: There are different screening tests that doctors use, as well as different cut-off levels to make a diagnosis.

Revision Information

  • Gestational diabetes mellitus (GDM). EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/ . Updated July 11, 2012. Accessed August 17, 2012.

  • Screening for gestational diabetes mellitus. The Society of Obstetricians and Gynaecologists of Canada website. Available at: http://www.sogc.org/guidelines/public/121E-CPG-November2002.pdf . Published November 2002. Accessed August 20, 2012.

  • What I need to know about gestational diabetes. National Diabetes Information Clearinghouse (NDIC) website. Available at: http://diabetes.niddk.nih.gov/dm/pubs/gestational/#7 . Updated December 6, 2011. Accessed August 17, 2012.