Endocrine & metabolic · UKMLA & AKT
Gestational diabetes mellitus
A free high-yield preview for the UKMLA Applied Knowledge Test, covering how to recognise this condition. The full SA Note notes add investigations, management and complications, with practice questions on this topic.
Key high-yield points
- GDM = carbohydrate intolerance first recognised or developing during pregnancy - distinct from pre-existing diabetes
- Gold standard: 75 g oral glucose tolerance test (OGTT) after ≥8 h overnight fast - fasting + 2-hour glucose
- NICE diagnostic thresholds (pregnancy-specific):
- Fasting glucose ≥5.6 mmol/L OR
- 2-hour glucose ≥7.8 mmol/L
- Either threshold alone is sufficient - a normal 2-hour result does not negate an elevated fasting glucose
- HbA1c is NOT used to screen for or diagnose GDM (altered red cell turnover in pregnancy makes it unreliable); useful in first trimester only to identify pre-existing undiagnosed diabetes
These thresholds differ from non-pregnant criteria (pre-diabetes, IGT, T2DM) - a common exam trap. In pregnancy, fasting ≥5.6 mmol/L = GDM regardless of the 2-hour result.
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