A 32-year-old woman with a history of pelvic inflammatory disease 2 years ago presents with 8 weeks of amenorrhoea and mild lower abdominal pain. Vital signs are stable. Serum β-hCG is 8,500 mIU/mL. Transvaginal ultrasound shows an empty uterus and a 2.5 cm mass in the left adnexa with free fluid in the pouch of Douglas. What is the most appropriate next step in management?

Explanation

## Management of Unruptured Ectopic Pregnancy ### Clinical Assessment: Haemodynamically Stable **Key Point:** This patient is haemodynamically stable with a confirmed unruptured ectopic pregnancy. She is a candidate for **medical management with methotrexate**, which is the preferred first-line treatment for appropriately selected cases. ### Eligibility Criteria for Medical Management | Criterion | Patient Status | Met? | |-----------|----------------|------| | Haemodynamic stability | BP normal, HR normal | ✓ | | No signs of rupture | Mild pain, no shock | ✓ | | β-hCG level | 8,500 mIU/mL | ✓ (typically <100,000) | | Ectopic mass size | 2.5 cm | ✓ (typically <4 cm) | | No contraindications to MTX | Not stated; assume none | ✓ | | Reliable follow-up | Not stated; assume yes | ✓ | ### Methotrexate Protocols **High-Yield:** Two regimens are commonly used: 1. **Single-dose MTX:** 50 mg/m² IM - Success rate: 88–96% (β-hCG <5,000) - Faster recovery, fewer side effects - Preferred if β-hCG <5,000 mIU/mL 2. **Multi-dose MTX:** 1 mg/kg IM on days 1, 3, 5, 7 (with folinic acid rescue on days 2, 4, 6, 8) - Success rate: 94–98% - Preferred if β-hCG >5,000 mIU/mL or high risk of failure **Clinical Pearl:** This patient's β-hCG of 8,500 mIU/mL is in the intermediate range; either protocol is reasonable, but multi-dose MTX may have slightly higher success. Shared decision-making is essential. ### Mechanism of Methotrexate Methotrexate is a **dihydrofolate reductase inhibitor** that: - Inhibits DNA synthesis in rapidly dividing cells (trophoblast) - Causes trophoblastic necrosis and resorption - Allows tubal preservation (salpingostomy equivalent) ### Follow-up Protocol After MTX 1. Serum β-hCG on day 4 post-injection 2. If decline <15%, repeat MTX dose 3. Then weekly β-hCG until undetectable 4. Contraception mandatory (teratogenic drug) 5. Avoid alcohol, NSAIDs, and folate antagonists during treatment **Mnemonic: SAFE-MTX** - **S**table haemodynamics - **A**ccurate diagnosis (ultrasound-confirmed) - **F**ew contraindications (renal/liver disease, immunosuppression) - **E**arly presentation (unruptured) - **M**ass <4 cm - **T**rusting patient (reliable follow-up) - **X** (hCG not excessively high, typically <100,000) [cite:Williams Obstetrics 26e Ch 19; ACOG Practice Bulletin 193]