A 32-year-old woman with a history of pelvic inflammatory disease presents with a 5-week amenorrhea, mild right 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 no intrauterine gestational sac, a 2.5 cm gestational sac in the right fallopian tube with a yolk sac, and no free fluid. The patient is reliable and willing for close follow-up. Which of the following is the most appropriate management?

Explanation

## Clinical Assessment This patient has an **unruptured tubal ectopic pregnancy** with hemodynamic stability and favorable conditions for medical management. ### Diagnostic Confirmation - **Absent intrauterine gestational sac** + **tubal gestational sac with yolk sac** = confirmed ectopic pregnancy - **Hemodynamically stable:** Normal vital signs, mild symptoms - **No rupture signs:** No free fluid, no severe pain, normal heart rate - **β-hCG 3,200 mIU/mL:** Appropriate for early ectopic pregnancy ## Management Decision Framework ```mermaid flowchart TD A[Unruptured ectopic pregnancy]:::outcome --> B{Hemodynamically stable?}:::decision B -->|Yes| C{Patient factors & β-hCG?}:::decision C -->|Reliable, β-hCG < 5000| D[Medical management]:::action C -->|Unreliable or β-hCG > 5000| E[Surgical management]:::action D --> F[Methotrexate single dose]:::action E --> G[Laparoscopic salpingostomy/ectomy]:::action B -->|No - Rupture| H[Emergency surgery]:::urgent ``` ### Why Methotrexate Is Optimal Here **Key Point:** Single-dose methotrexate is the **first-line medical treatment** for unruptured ectopic pregnancy when: 1. Patient is hemodynamically stable 2. β-hCG < 5,000 mIU/mL (ideally < 3,500) 3. Ectopic mass < 3.5 cm 4. No free fluid 5. Patient is reliable and can comply with follow-up **High-Yield:** Methotrexate mechanism in ectopic pregnancy: - Inhibits dihydrofolate reductase → blocks DNA synthesis - Arrests rapidly dividing trophoblastic cells - Allows resorption of ectopic tissue over 4–7 days - Success rate: 88–96% with single dose when criteria met **Clinical Pearl:** This patient meets **all criteria** for medical management: - Hemodynamically stable - β-hCG 3,200 (< 5,000 threshold) - Gestational sac 2.5 cm (< 3.5 cm) - No free fluid - Reliable and willing for close follow-up ## Post-Methotrexate Monitoring | Timeline | Action | |----------|--------| | Day 0 | Baseline β-hCG, CBC, LFTs, renal function | | Day 4 | Repeat β-hCG (should drop ≥15%) | | Day 7 | Repeat β-hCG (should drop ≥15% from day 4) | | Weekly | β-hCG until undetectable | | Ultrasound | Weekly until ectopic mass resolves | **Mnemonic: METHOTREXATE CRITERIA — "STABLE & SMALL"** - **S**table hemodynamically - **T**ubal mass < 3.5 cm - **A**bsent free fluid - **B**-hCG < 5,000 - **L**ow risk (no contraindications) - **E**xpectant patient (reliable follow-up) [cite:Jeffcoate's Principles of Gynaecology 8e Ch 8; RCOG Green-top Guideline 21]