What is the next step for a 21-year-old pregnant woman with a glucose level of 154 mg/dL after a non-fasting 50-gram glucose screening test (Glucose Challenge Test, GCT)?

From the Guidelines

Based on GL's 50-gram glucose screening test result of 154 mg/dL, the appropriate action is to refer her for a fasting 100-gram oral glucose tolerance test to determine if she has gestational diabetes. This recommendation is guided by the most recent and highest quality study, which suggests that a plasma glucose level of ≥130,135, or 140 mg/dL after a 50-g glucose load test indicates the need for further testing with a 100-g OGTT 1. The 50-gram test is only a screening tool, not diagnostic on its own, and a result above the threshold indicates the need for the more definitive 3-hour, 100-gram glucose tolerance test.

Key Considerations for the 100-gram OGTT

• The test should be performed when the patient is fasting, typically after an overnight fast of at least 8 hours.
• The patient will consume 100 grams of glucose, and then have her blood glucose measured at 1,2, and 3 hours afterward.
• Diagnosis of gestational diabetes requires at least two abnormal values on this test, based on the Carpenter-Coustan criteria, which are:
  • Fasting: 95 mg/dL (5.3 mmol/L)
  • 1 hour: 180 mg/dL (10.0 mmol/L)
  • 2 hours: 155 mg/dL (8.6 mmol/L)
  • 3 hours: 140 mg/dL (7.8 mmol/L) 1.

Importance of Accurate Diagnosis

Accurate diagnosis of gestational diabetes is crucial to prevent complications for both mother and baby. The stepped approach of initial screening with a 50-gram glucose test followed by a 100-gram OGTT for those with elevated results helps avoid both false positives and false negatives, ensuring proper identification of women who need additional monitoring and management during pregnancy 1.

From the Research

Gestational Diabetes Diagnosis

Based on the provided evidence, the following steps can be taken for GL, a 21-year-old pregnant woman with a non-fasting 50-gram screening test result of 154 mg/dL:

• The American College of Obstetricians and Gynecologists (ACOG) recommends a cutoff value of 140 mg/dL for the 50-g glucose challenge test, but some studies suggest using a cutoff of 155 mg/dL for high-risk women 2.
• Given GL's result of 154 mg/dL, which is close to the suggested cutoff of 155 mg/dL, it is essential to consider her individual risk factors and medical history.
• According to the study by 3, women with mild hyperglycemia, even below the current diagnostic criteria for gestational diabetes, may benefit from management to improve pregnancy outcomes.

Next Steps

Considering GL's screening test result, the following options can be considered:

• Refer for a fasting 100 gram oral glucose tolerance test: This is a common next step for women with a screening test result close to the cutoff value, as it can provide a more accurate diagnosis of gestational diabetes 2, 3.
• Diagnosis of gestational diabetes and referral to a high-risk obstetrician: If the 100-g OGTT confirms the diagnosis of gestational diabetes, GL should be referred to a high-risk obstetrician for further management and care.
• Negative for gestational diabetes and continue routine pregnancy care: If the 100-g OGTT results are normal, GL can continue with routine pregnancy care, but her healthcare provider should continue to monitor her glucose levels and adjust her care plan as needed.

Considerations

When deciding on the next steps for GL, her healthcare provider should consider the following:

• Individual risk factors: GL's age, medical history, and other risk factors should be taken into account when interpreting her screening test result and determining the best course of action.
• Current guidelines: The healthcare provider should be aware of current guidelines and recommendations for gestational diabetes screening and diagnosis, such as those from ACOG and other reputable organizations.
• Patient education and support: GL should be educated about the risks and consequences of gestational diabetes and provided with support and resources to manage her condition, if diagnosed.