A 31-year-old woman presents at 7 weeks gestation with vaginal bleeding and an adnexal mass. Beta-hCG is 3,200 mIU/mL. Transvaginal ultrasound shows an empty uterus and a 2.5 cm left adnexal mass with a yolk sac sign. She is hemodynamically stable. Methotrexate single-dose protocol (50 mg/m²) is administered. On day 4, she reports increased pain. Beta-hCG on day 4 is 3,600 mIU/mL (increase from baseline). What is the most appropriate interpretation?
- A Expected post-treatment hCG surge; wait for day 7 level for treatment success assessment ✓
- B Methotrexate failure—immediate surgical intervention required
- C Ectopic has ruptured—emergency laparotomy required
- D Heterotopic pregnancy—intrauterine pregnancy needs to be evaluated
Explanation
After single-dose intramuscular methotrexate for ectopic pregnancy, an initial rise in beta-hCG between days 1 and 4 is a well-recognized and EXPECTED phenomenon, occurring in up to 80% of successful cases. This 'hCG surge' results from continued trophoblast cell lysis releasing stored hCG, not from treatment failure. Treatment is assessed at day 7: if hCG falls ≥15% from day 4 to day 7, treatment is considered successful. If it does not fall ≥15%, a second dose is given or surgical intervention is considered. Increased cramping is also expected (separation pain). Rupture is suspected if there is increasing pain with hemodynamic instability, hemoperitoneum, or significant increase in adnexal mass size rather than a simple hCG rise.
Reference: Williams Obstetrics, 26th ed.
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Written and medically reviewed by the StethoPrep medical team.