A 28-year-old primigravida at 24 weeks of gestation is diagnosed with gestational diabetes mellitus (GDM) on 75-g oral glucose tolerance test (OGTT). Regarding the management and screening of GDM, all of the following statements are true EXCEPT:

Question

Accepted Answer

A. All pregnant women should undergo universal screening for GDM at 16–18 weeks of gestation. ## Analysis of GDM Screening and Management

### Correct Answer: Universal Screening at 16–18 Weeks

**Key Point:** The standard screening for GDM is performed at **24–28 weeks of gestation**, NOT at 16–18 weeks. This timing reflects the physiological insulin resistance that develops in the second and third trimesters.

### Why Other Options Are Correct

| Statement | Evidence |
|-----------|----------|
| **Fasting glucose ≥126 mg/dL on OGTT is diagnostic** | WHO/IADPSG criteria: fasting ≥126 mg/dL (or ≥7.0 mmol/L) on 75-g OGTT is one of three diagnostic thresholds for GDM [cite:IADPSG 2010] |
| **Metformin is first-line pharmacological agent** | Metformin is safe in pregnancy, does not cross placenta significantly, and is recommended as first-line agent when lifestyle modification fails [cite:ACOG 2018] |
| **Insulin if glycemic targets unmet** | Insulin is the gold standard and mandatory if diet/exercise/metformin fail to achieve targets (fasting <95 mg/dL, 1-h postprandial <140 mg/dL, 2-h postprandial <120 mg/dL) |

### Screening Timeline

**High-Yield:** The two-step screening approach in many centres:
1. **24–28 weeks:** 50-g glucose challenge test (GCT) — non-fasting, any time of day
2. **If GCT ≥140 mg/dL:** Proceed to 75-g OGTT (fasting) for diagnosis

**Clinical Pearl:** Early screening (16–18 weeks) is reserved only for high-risk women (obesity, prior GDM, family history of diabetes, polycystic ovary syndrome) to detect pre-existing type 2 diabetes, not routine GDM screening.

**Warning:** Confusing the screening week (24–28 weeks) with early risk assessment (16–18 weeks in high-risk groups) is a common exam trap.

Answer

B. Metformin is safe and recommended as first-line pharmacological agent in GDM

Answer

C. Fasting blood glucose ≥126 mg/dL on OGTT is diagnostic of GDM

Answer

D. Insulin therapy is indicated if glycemic targets are not achieved with diet and exercise alone

Statement	Evidence
Fasting glucose ≥126 mg/dL on OGTT is diagnostic	WHO/IADPSG criteria: fasting ≥126 mg/dL (or ≥7.0 mmol/L) on 75-g OGTT is one of three diagnostic thresholds for GDM IADPSG 2010
Metformin is first-line pharmacological agent	Metformin is safe in pregnancy, does not cross placenta significantly, and is recommended as first-line agent when lifestyle modification fails ACOG 2018
Insulin if glycemic targets unmet	Insulin is the gold standard and mandatory if diet/exercise/metformin fail to achieve targets (fasting <95 mg/dL, 1-h postprandial <140 mg/dL, 2-h postprandial <120 mg/dL)

A 28-year-old primigravida at 24 weeks of gestation is diagnosed with gestational diabetes mellitus (GDM) on 75-g oral glucose tolerance test (OGTT). Regarding the management and screening of GDM, all of the following statements are true EXCEPT:

Explanation

Analysis of GDM Screening and Management

Correct Answer: Universal Screening at 16–18 Weeks

Why Other Options Are Correct

Screening Timeline

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