From the Guidelines
Approximately 15-20% of pregnant women test positive during the initial glucose tolerance screening test. This screening, typically performed between 24-28 weeks of pregnancy, involves drinking a glucose solution and having blood drawn an hour later to measure blood sugar levels. A positive result (usually defined as a blood glucose level of 140 mg/dL or higher) doesn't necessarily mean the woman has gestational diabetes; rather, it indicates the need for a follow-up diagnostic test called the oral glucose tolerance test (OGTT) 1. Of those who test positive on the initial screening, only about one-third will actually be diagnosed with gestational diabetes after the confirmatory OGTT. The screening test has intentionally high sensitivity to minimize missed cases, which explains the relatively high rate of positive results. Factors that increase the likelihood of a positive screening include:
- Advanced maternal age
- Obesity
- Family history of diabetes
- Previous gestational diabetes
- Certain ethnic backgrounds with higher diabetes risk 1. The prevalence of gestational diabetes mellitus (GDM) in the United States is about 6% to 7%, affecting approximately 240,000 of 4 million annual births 1. The diagnosis of GDM is made when any of the following plasma glucose values are exceeded: fasting ≥ 92 mg/dL, 1 hour ≥ 180 mg/dL, or 2 hours ≥ 153 mg/dL 1.
From the Research
Prevalence of Gestational Diabetes Mellitus
- The prevalence of gestational diabetes mellitus (GDM) varies across studies and diagnostic criteria, ranging from 2 to 50 percent 2.
- According to the American Diabetes Association (75 g) criteria, the prevalence of GDM is between 2 and 19 percent 2.
- The Carpenter and Coustan criteria report a prevalence of 3.6 to 38 percent, while the National Diabetes Data Group criteria show a range of 1.4 to 50 percent 2.
- The World Health Organization criteria indicate a prevalence of 2 to 24.5 percent 2.
Screening and Diagnosis of GDM
- A two-step approach (1-hour 50 g glucose challenge test followed by 3-hour 100 g oral glucose tolerance test) has been widely used for GDM screening and diagnosis 3.
- A one-step approach (75 g oral glucose tolerance test) is also recommended as an option for the diagnosis of GDM after 2010 3.
- The 50 g oral glucose challenge test with a glucose threshold of 130 mg/dL versus 140 mg/dL improves sensitivity and reduces specificity 2.
Percentage of Women Testing Positive
- The exact percentage of women testing positive during pregnancy glucose tolerance screening test is not directly stated in the provided studies.
- However, the studies suggest that the prevalence of GDM varies widely depending on the diagnostic criteria used, ranging from 2 to 50 percent 2.