A 32-year-old woman (G3P2) with a history of pelvic inflammatory disease presents with 8 weeks of amenorrhoea, mild lower abdominal pain, and light vaginal spotting. Vital signs are stable (BP 118/76, HR 82/min). Serum β-hCG is 3,200 mIU/mL. Transvaginal ultrasound shows an empty uterine cavity, no free fluid, and a 2.2 cm gestational sac-like structure in the right fallopian tube with yolk sac but no fetal pole. The patient is reliable and willing to comply with follow-up. What is the most appropriate management?

Explanation

## Clinical Diagnosis This is an **unruptured tubal ectopic pregnancy** in a haemodynamically stable patient with appropriate criteria for medical (methotrexate) management. ## Criteria for Medical Management of Ectopic Pregnancy | Criterion | This Patient | Status | |-----------|--------------|--------| | **Haemodynamic stability** | BP 118/76, HR 82 | ✓ Stable | | **No rupture** | No free fluid on ultrasound | ✓ Unruptured | | **β-hCG level** | 3,200 mIU/mL | ✓ <5,000 (ideal <4,000) | | **Ectopic mass size** | 2.2 cm | ✓ <3.5 cm | | **No fetal cardiac activity** | Yolk sac present, no FPM | ✓ Favourable | | **Reliable follow-up** | Patient states compliance | ✓ Essential | | **Accessible hospital** | Implied | ✓ Required | **High-Yield:** When all criteria are met, **single-dose methotrexate (50 mg IM)** is the first-line treatment because it: 1. Avoids surgery and general anaesthesia 2. Preserves tubal anatomy and function 3. Has >90% success rate when β-hCG <5,000 mIU/mL 4. Is cost-effective ## Mechanism of Methotrexate **Key Point:** Methotrexate is a **dihydrofolate reductase inhibitor** that blocks DNA synthesis in rapidly dividing trophoblastic cells. It causes: - Trophoblastic necrosis and resorption - Regression of the ectopic pregnancy - Gradual decline in β-hCG over 7–14 days **Clinical Pearl:** β-hCG should decline by ≥15% between days 4 and 7 post-injection. If it rises or plateaus, the pregnancy is progressing and surgery becomes necessary. ## Why Not Salpingostomy? Although laparoscopic salpingostomy is also a valid option for unruptured ectopic with stable haemodynamics, **medical management is preferred** because: - It avoids operative risk (anaesthesia, bleeding, infection) - Tubal patency rates are similar (60–80% with both approaches) - Repeat ectopic risk is slightly lower with methotrexate - Patient is ideal candidate (reliable, compliant, accessible) **Mnemonic — STABLE criteria for medical management:** **S**table vitals, **T**ubal location, **A**ccurate dating, **B**-hCG <5,000, **L**ow mass size, **E**ligible for follow-up. ## Why Not Expectant Management? Expectant management (observation without treatment) is appropriate **only** when: - β-hCG is very low (<1,000–1,500 mIU/mL) - Ectopic mass is tiny (<1 cm) - Patient is at very high risk from methotrexate (e.g., renal disease, hepatic disease) This patient has β-hCG 3,200 and a 2.2 cm mass — expectant management carries unacceptable risk of rupture during the observation period. ## Why Not Salpingectomy? Salpingectomy is reserved for: - Ruptured ectopic (this is unruptured) - Haemodynamic instability (this patient is stable) - Recurrent ectopic in the same tube - Patient refusal of medical/conservative management Removing a healthy fallopian tube in a young, stable patient with an unruptured ectopic is unnecessarily morbid.