BC ADM Gestational & Pregestational Diabetes Management 1 — Questions and Answers
Question 1: What is the recommended two-step screening approach for gestational diabetes mellitus (GDM) at 24-28 weeks?
- 50g glucose challenge test; if ≥140 mg/dL, proceed to 3-hour 100g OGTT (Correct answer)
- 75g OGTT with a single fasting value threshold
- Fasting glucose at first prenatal visit followed by HbA1c at 24 weeks
- Direct 3-hour 100g OGTT without prior screening
Correct answer: 50g glucose challenge test; if ≥140 mg/dL, proceed to 3-hour 100g OGTT
The two-step approach uses a non-fasting 50g GCT at 24-28 weeks; a 1-hour result ≥140 mg/dL triggers the diagnostic 3-hour 100g OGTT.
Question 2: Using Carpenter-Coustan criteria for the 3-hour 100g OGTT, how many abnormal values are required to diagnose GDM?
- 1 or more values meeting threshold
- 2 or more values meeting threshold (Correct answer)
- 3 or more values meeting threshold
- All 4 values must meet threshold
Correct answer: 2 or more values meeting threshold
GDM is diagnosed when 2 or more of the 4 timed values (fasting, 1-hr, 2-hr, 3-hr) meet or exceed the Carpenter-Coustan thresholds.
Question 3: Which glucose thresholds define GDM diagnosis using the one-step 75g OGTT (IADPSG/ADA criteria)?
- Fasting ≥92, 1-hr ≥180, or 2-hr ≥153 mg/dL (any one value) (Correct answer)
- Fasting ≥100, 1-hr ≥190, or 2-hr ≥160 mg/dL (any two values)
- Fasting ≥95, 1-hr ≥180, and 2-hr ≥155 mg/dL (all three values)
- Fasting ≥126 or 2-hr ≥200 mg/dL
Correct answer: Fasting ≥92, 1-hr ≥180, or 2-hr ≥153 mg/dL (any one value)
The IADPSG one-step 75g OGTT diagnoses GDM when any single value meets or exceeds fasting ≥92, 1-hr ≥180, or 2-hr ≥153 mg/dL.
Question 4: What is the primary pathophysiologic mechanism underlying gestational diabetes mellitus?
- Autoimmune destruction of pancreatic beta cells triggered by pregnancy hormones
- Insulin resistance amplified by placental hormones combined with inadequate beta-cell compensation (Correct answer)
- Excess glucagon secretion from maternal alpha cells during the second trimester
- Decreased hepatic glucose production due to fetal glucose uptake
Correct answer: Insulin resistance amplified by placental hormones combined with inadequate beta-cell compensation
GDM results from physiologic pregnancy-related insulin resistance—amplified by placental hormones such as human placental lactogen—combined with insufficient compensatory beta-cell insulin secretion.
Question 5: Which of the following is NOT a recognized risk factor for gestational diabetes mellitus?
- Pre-pregnancy BMI greater than 25 kg/m²
- Previous delivery of a macrosomic infant (>9 lbs)
- Nulliparity (no prior pregnancies) (Correct answer)
- First-degree relative with type 2 diabetes
Correct answer: Nulliparity (no prior pregnancies)
Nulliparity is not a recognized risk factor for GDM; major risk factors include obesity, prior macrosomic infant, family history of T2DM, prior GDM, and certain ethnic backgrounds.
Question 6: When should screening for undiagnosed pregestational diabetes occur in pregnant women with risk factors?
- At the first prenatal visit using standard adult diabetes diagnostic criteria (Correct answer)
- At 24-28 weeks using the standard GDM two-step protocol
- At 16-20 weeks with a 75g OGTT regardless of risk factors
- Only if HbA1c exceeds 6.0% at any prenatal visit
Correct answer: At the first prenatal visit using standard adult diabetes diagnostic criteria
Women with risk factors for undiagnosed type 2 diabetes should be screened at the first prenatal visit using standard non-pregnancy diagnostic thresholds (HbA1c, fasting glucose, or 75g OGTT).
Question 7: A pregnant woman at 26 weeks has a 1-hour 50g GCT result of 158 mg/dL and subsequently a 3-hour 100g OGTT with only one value above the Carpenter-Coustan threshold. What is the appropriate clinical action?
- Diagnose GDM and initiate lifestyle modifications immediately
- Consider an individualized approach; one abnormal value may indicate impaired glucose tolerance warranting close follow-up (Correct answer)
- Repeat the 3-hour OGTT in 4 weeks
- Initiate insulin therapy given the high GCT value
Correct answer: Consider an individualized approach; one abnormal value may indicate impaired glucose tolerance warranting close follow-up
One abnormal OGTT value does not meet Carpenter-Coustan criteria for GDM but indicates impaired glucose tolerance; clinical guidelines support individualized dietary counseling and close monitoring in this scenario.
BC ADM Gestational & Pregestational Diabetes Management 1
What is the recommended two-step screening approach for gestational diabetes mellitus (GDM) at 24-28 weeks?