## 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.
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