A 32-year-old woman with a history of pelvic inflammatory disease presents with 8 weeks of amenorrhea, mild lower abdominal pain, and light vaginal spotting. Vital signs are stable (BP 110/70, HR 88/min). Serum β-hCG is 2800 mIU/mL. Transvaginal ultrasound shows no gestational sac in the uterus, a 2.5 cm complex mass in the left adnexa, and no free fluid. She desires future fertility. What is the most appropriate management?

Explanation

## Clinical Diagnosis and Rationale **Key Point:** This is a hemodynamically stable, unruptured ectopic pregnancy with favorable criteria for medical management — the patient's desire for future fertility makes methotrexate an ideal first-line option. ### Why Methotrexate Is the Best Choice The patient meets all criteria for medical (medical) management: | Criterion | Patient Status | |-----------|----------------| | Hemodynamic stability | ✓ BP 110/70, HR 88 | | No rupture signs | ✓ No free fluid, mild pain | | β-hCG level | ✓ 2800 mIU/mL (<5000) | | Ectopic mass size | ✓ 2.5 cm (<3.5 cm) | | Desire for fertility | ✓ Yes | | No contraindications to MTX | ✓ (assume normal renal/hepatic function) | **High-Yield:** Methotrexate is a **folate antagonist** that inhibits dihydrofolate reductase, blocking DNA synthesis and causing trophoblastic cell death. It is the preferred first-line agent in hemodynamically stable, unruptured ectopic pregnancies because: 1. Preserves tubal anatomy (vs. salpingectomy) 2. Success rate 88–96% with single-dose regimen 3. Allows future intrauterine pregnancy 4. Avoids surgical morbidity ### Methotrexate Dosing and Monitoring ```mermaid flowchart TD A[Unruptured ectopic pregnancy]:::outcome --> B[Single-dose MTX: 1 mg/kg IM]:::action B --> C[Check β-hCG on day 4]:::action C --> D{β-hCG decline ≥15%?}:::decision D -->|Yes| E[Repeat β-hCG weekly until undetectable]:::action D -->|No| F[Second MTX dose or consider surgery]:::action E --> G[Counsel: avoid alcohol, NSAIDs, folate antagonists]:::action G --> H[Contraception for 3 months]:::action H --> I[Resumption of fertility attempts]:::action ``` **Clinical Pearl:** The **day-4 β-hCG** is the critical checkpoint. A decline of ≥15% from baseline predicts success; <15% decline suggests treatment failure and need for second dose or surgery. **Mnemonic:** **MTX-HCG** — **M**ethotrexate for **T**rophoblastic e**X**pulsion; check **HCG** on day 4. ## Why Other Options Are Wrong | Option | Why Incorrect | |--------|---------------| | Emergency laparoscopy + salpingectomy | Surgical approach is reserved for hemodynamically unstable, ruptured, or failed medical management cases. This patient is stable and desires fertility — salpingectomy is unnecessarily morbid. | | Dilation and curettage | D&C cannot evacuate an ectopic pregnancy; the pregnancy is in the fallopian tube, not the uterus. This approach is ineffective and delays definitive treatment. | | Expectant management alone | While expectant management is an option in very select cases (β-hCG <1000, declining trend, reliable follow-up), this patient's β-hCG of 2800 and adnexal mass make active medical management safer. | **Warning:** Do not confuse **medical management of ectopic pregnancy** (methotrexate) with **medical management of miscarriage** (expectant or medical with misoprostol). Ectopic pregnancies require methotrexate, not misoprostol. [cite:Jeffcoate's Principles of Gynaecology 8e Ch 12; RCOG Green-top Guideline 21]