In a woman with chronic hypertension who develops superimposed pre-eclampsia at 36 weeks, which feature MOST reliably distinguishes superimposed pre-eclampsia from worsening chronic hypertension alone?
- A Diastolic blood pressure persistently above 100 mmHg despite antihypertensive therapy
- B Rise in baseline blood pressure of more than 30/15 mmHg
- C New-onset thrombocytopenia (platelets <100,000/mm³) or new elevated serum creatinine >1.1 mg/dL ✓
- D Proteinuria exceeding 300 mg per 24 hours in a previously non-proteinuric patient
Correct answer: C. New-onset thrombocytopenia (platelets <100,000/mm³) or new elevated serum creatinine >1.1 mg/dL
Explanation
ACOG 2019 guidance specifies that in a woman with chronic hypertension, the development of new thrombocytopenia (platelets <100,000/mm³) or new renal insufficiency (creatinine >1.1 mg/dL or doubling of baseline creatinine without other explanation) is the MOST reliable indicator of superimposed pre-eclampsia. New-onset proteinuria alone is less reliable due to pre-existing renal disease, and the 30/15 mmHg rule was removed from ACOG criteria in 2002. The key severe-feature end-organ markers are thus most diagnostically specific.
Reference: Williams Obstetrics, 26th ed.
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