The 1 hour Oral Glucose Tolerance Test
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The Sweet Success Program of California recommends that all pregnant women be screened for gestational diabetes at 24-28 weeks, or earlier if risk factors are present. Screening is usually done using the 1 hour oral glucose tolerance test.

Patients should be screened at their first prenatal visit if any of the following risk factors are present:

  • Family history of diabetes in first-degree relatives
  • Previous history of:
    • Gestational diabetes
    • Macrosomia
    • Unexplained stillbirth
    • Malformed infant
  • >25 years of age
  • BMI >30
  • Glucosuria > 2+
  • Member of an ethnic/racial group with a high prevalence of diabetes (i.e., Hispanic-American, Native American, Asian-American, African-American, Pacific Islander, or of Indigenous Australian ancestry)
  • Taking medications causing hyperglycemia (i.e. terbutaline,prednisone)

A plasma concentration >200 mg/dl (11.1 mmol/l) under any conditions outside of the context of a formal glucose challenge test or a fasting plasma glucose concentration  >126 mg/dl (7.0 mmol/l) warrants confirmatory testing as quickly as possible.

1 hour Oral Glucose Tolerance Test (OGTT)
The test can be done at any time of the day. Fasting is not required.
Administer a 50 gram glucose load followed by a one-hour plasma glucose:

    • Negative test if : < 140 mg/dl
    • Positive test if: > 140 mg/dl


  • Values 140 mg/dl to 179 mg/dl require follow-up with a 3-hour 100 gram oral glucose tolerance test (OGTT) within one week.
  • If the patient has a screening value > 180 mg/dl, a fasting blood sugar should be checked as soon as possible.

  • An elevated fasting value of > 95 and screening test > 180 mg/dl provides two abnormal values, and treatment for gestational diabetes is recommended.
  • If the fasting value is less than 95 then proceed with the 3 hour OGTT.

Women who were evaluated early during their pregnancy and found to be normoglycemic should have screening repeated at 24 to 28 weeks.

  

    REFERENCE:
    *Guidelines for Care, California Diabetes and Pregnancy Program,2002

Created: 12/18/2002
Updated: 11/2/2004
Updated: 6/26/2007

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