A 32-year-old woman with a history of pelvic inflammatory disease presents with 6 weeks amenorrhea and mild right-sided pelvic pain. Urine pregnancy test is positive. Transvaginal ultrasound shows an empty uterus and a 2.8 cm mass in the right adnexa without fetal heart activity. Serum β-hCG is 3,200 IU/L. Hemodynamic parameters are normal (BP 120/80 mmHg, HR 82/min). What is the most appropriate next step in management?

Explanation

## Clinical Presentation Analysis This patient has an **unruptured, hemodynamically stable ectopic pregnancy** that is an ideal candidate for **medical management with methotrexate**. ## Criteria for Medical Management — All Met | Criterion | This Patient | Status | |-----------|--------------|--------| | Hemodynamic stability | BP 120/80, HR 82 | ✓ Stable | | β-hCG level | 3,200 IU/L | ✓ <5,000 (optimal) | | Ectopic mass size | 2.8 cm | ✓ <3.5 cm | | Free pelvic fluid | None | ✓ Absent | | Fetal heart activity | Absent | ✓ No FHR | | Reliable follow-up | Implied | ✓ Essential | ## Management Algorithm ```mermaid flowchart TD A[Unruptured ectopic pregnancy]:::outcome --> B{Hemodynamically stable?}:::decision B -->|Yes| C{Candidate for medical Rx?}:::decision C -->|Yes: β-hCG <5000, no FHR| D[Single-dose methotrexate 50 mg/m² IM]:::action C -->|No: high β-hCG, large mass| E[Surgical management]:::action D --> F[Serial β-hCG on days 4, 7]:::action F --> G{β-hCG declining >15%?}:::decision G -->|Yes| H[Weekly monitoring until undetectable]:::action G -->|No| I[Repeat methotrexate or surgery]:::action ``` ## Key Point: **Single-dose methotrexate is first-line for unruptured, hemodynamically stable ectopic pregnancy** meeting the criteria above. It: - Inhibits dihydrofolate reductase → blocks DNA synthesis in rapidly dividing trophoblastic cells - Achieves tubal preservation in ~90% of cases - Avoids surgical morbidity - Allows future fertility ## High-Yield: **Methotrexate dosing and monitoring:** - **Single-dose regimen:** 50 mg/m² IM (most commonly used) - **Multi-dose regimen:** 1 mg/kg IM on days 0, 2, 4, 6 (used if β-hCG >5,000 or single-dose fails) - **Success rate:** ~90% with single dose if β-hCG <1,000; ~80% if β-hCG 1,000–5,000 - **Follow-up:** β-hCG on day 4 and day 7; should decline by ≥15% between days 4–7 - **Contraindications:** Active pulmonary/renal disease, immunodeficiency, blood dyscrasias, peptic ulcer disease ## Clinical Pearl: **Fetal heart activity is a relative contraindication** to medical management — even if hemodynamically stable, the presence of FHR suggests higher viability and rupture risk; surgical management is preferred. Absence of FHR in this patient makes medical management safer. ## Warning: ~~Diagnostic laparoscopy~~ is **not** the next step. Diagnosis is already confirmed by ultrasound (empty uterus + adnexal mass + positive hCG). Laparoscopy is reserved for diagnostic uncertainty, not for management of a confirmed ectopic pregnancy. [cite:Cunningham 26e Ch 19; ACOG Practice Bulletin 193]