Recommended GDM Screening for This Patient
This patient should undergo a 75g oral glucose tolerance test (OGTT) at 24-28 weeks gestation (option C), which is the standard timing and method for universal GDM screening. 1, 2
Rationale for Standard Screening Timing
At 23 weeks gestation, this patient does not meet criteria for early screening despite having a family history of Type 2 Diabetes Mellitus. The key considerations are:
Family history alone (mother with T2DM) is not sufficient to warrant immediate early screening at this visit, as she lacks other high-risk criteria such as BMI ≥30 kg/m², prior GDM history, or previous delivery of a macrosomic infant 1, 2
Universal screening between 24-28 weeks is recommended for all pregnant women not previously diagnosed with diabetes, regardless of risk factors 3, 1
The 75g OGTT is the preferred one-step approach endorsed by the American Diabetes Association and International Diabetes Federation, with diagnostic thresholds of fasting ≥92 mg/dL, 1-hour ≥180 mg/dL, or 2-hour ≥153 mg/dL (any single value being diagnostic) 1, 4, 5
Why Other Options Are Incorrect
Option A (HbA1c at this visit): HbA1c is not recommended for GDM screening or diagnosis during pregnancy, though it may be useful for detecting pre-existing diabetes in early pregnancy 6
Option B (Random blood sugar at this visit): Random glucose testing is not a standard screening method for GDM and lacks the sensitivity and specificity of the OGTT 3
Option D (3-hour glucose tolerance test at 28-32 weeks): This represents the second step of the two-step approach (100g OGTT) used only after a positive 50g glucose challenge test, not as initial screening 1, 2
Clinical Advantages of the 75g OGTT
The one-step 75g OGTT approach offers several benefits:
- Faster diagnosis with results available from a single test 4, 6
- Better patient tolerance compared to the 100g load 6
- Outcome-based criteria derived from the landmark HAPO study demonstrating correlation with adverse pregnancy outcomes 4, 7
- International consensus supporting this methodology 4, 6
Important Follow-Up Considerations
Postpartum screening is mandatory: All women diagnosed with GDM should undergo 75g OGTT at 4-12 weeks postpartum using non-pregnant diagnostic criteria 1, 5
Lifelong surveillance required: Women with GDM history need screening for diabetes or prediabetes at least every 3 years 3, 1
Family history increases her baseline risk: While not triggering early screening, her maternal history of T2DM does place her at higher risk for developing GDM and future diabetes 1, 2