## Timing of Gestational Diabetes Screening **Key Point:** The oral glucose tolerance test (OGTT) or random blood glucose screening for gestational diabetes mellitus (GDM) is performed at **24–28 weeks of gestation** in India, as per ICMR and FOGSI guidelines. ### Rationale for 24–28 Weeks 1. **Physiological basis**: Insulin resistance peaks in the second and third trimester, making this the optimal window to detect GDM. 2. **Clinical outcome**: Early detection allows time for dietary and lifestyle interventions before fetal complications arise. 3. **Standard practice**: This timing aligns with international guidelines (WHO, ACOG) and is universally adopted in Indian antenatal care. ### Screening Protocol in India | Gestational Age | Test | Method | | --- | --- | --- | | 24–28 weeks | Random blood glucose or OGTT | Fasting + 2-hour post-load | | If RBG ≥140 mg/dL | Confirmatory OGTT | 75 g, 2-hour OGTT | | Diagnostic criteria | OGTT ≥140 mg/dL (2-hour value) | ICMR criteria | **High-Yield:** GDM screening at 24–28 weeks is a **cornerstone of antenatal care** in India; missing this window delays diagnosis and increases risk of macrosomia, polyhydramnios, and neonatal hypoglycemia. **Clinical Pearl:** Women with risk factors (obesity, family history of diabetes, previous GDM) may warrant earlier screening at 16–18 weeks, but routine screening remains 24–28 weeks.
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