A 28-year-old woman receives single-dose methotrexate (50 mg/m² IM) for an unruptured ampullary ectopic pregnancy. Serum β-hCG is measured on Day 4 and Day 7. Which of the following Day 4 to Day 7 β-hCG patterns indicates that medical treatment has FAILED and further intervention is required?
- A β-hCG falls by 8% from Day 4 to Day 7 ✓
- B β-hCG falls by 15% from Day 4 to Day 7
- C β-hCG rises by 5% from Day 4 to Day 7
- D β-hCG falls by 20% from Day 4 to Day 7
Correct answer: A. β-hCG falls by 8% from Day 4 to Day 7
Explanation
A decline of less than 15% between Day 4 and Day 7 constitutes treatment failure requiring either a second dose of methotrexate or surgical intervention. A rise also indicates failure, but option A (8% fall) meets the formal definition of suboptimal decline. A 15% fall or greater is considered adequate response. Option B is the minimum acceptable response, not failure.
Reference: Williams Obstetrics, 26th ed.
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Written and medically reviewed by the StethoPrep medical team.