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. Serum β-hCG is 3,200 mIU/mL. Transvaginal ultrasound shows no intrauterine gestational sac, a 2.5 cm mass in the left fallopian tube, and no free fluid. Vital signs are stable (BP 118/76, HR 82/min). Hemoglobin is 11.8 g/dL. She is counseled about all management options. What is the most appropriate next step?

Explanation

## Clinical Presentation & Diagnosis This patient has an **unruptured ectopic pregnancy** with hemodynamic stability and favorable conditions for medical management: **Key Point:** Unruptured ectopic pregnancy in a stable patient with β-hCG 3,200 mIU/mL (in the range 1,000–5,000) is ideal for medical management with methotrexate. Single-dose methotrexate is the first-line medical option when criteria are met. ## Criteria for Medical Management of Ectopic Pregnancy | Criterion | This Patient | Status | |-----------|--------------|--------| | Hemodynamic stability | BP 118/76, HR 82 | ✓ Met | | No rupture signs | No free fluid, stable Hb | ✓ Met | | β-hCG 1,000–5,000 | 3,200 mIU/mL | ✓ Met | | Ectopic mass <3.5 cm | 2.5 cm | ✓ Met | | No cardiac activity on imaging | Not documented but implied | ✓ Met | | Reliable for follow-up | Implied by presentation | ✓ Met | | No contraindications to MTX | No mention of renal/hepatic disease | ✓ Met | ## Why Single-Dose Methotrexate is Correct **High-Yield:** Single-dose methotrexate (50 mg/m² IM) is the preferred medical regimen for unruptured ectopic pregnancy with β-hCG <5,000 because: 1. **Efficacy:** Success rate 88–96% in appropriately selected cases 2. **Simplicity:** Single injection vs. multi-dose regimen 3. **Lower toxicity:** Fewer side effects than multi-dose methotrexate 4. **Cost-effective:** Reduces clinic visits and monitoring burden **Clinical Pearl:** Methotrexate works by inhibiting dihydrofolate reductase, blocking DNA synthesis in rapidly dividing trophoblastic cells. Resolution takes 7–14 days; β-hCG should decline by ≥15% between days 4 and 7. ## Why Other Options Are Wrong | Option | Reason | |--------|--------| | Immediate laparoscopy | Surgical management is reserved for hemodynamically unstable patients, those with rupture, or medical management failure. This patient is stable with an ideal candidate profile for medical management. Laparoscopy is more invasive and costly. | | Expectant management | While expectant management is an option in stable patients with β-hCG <1,000 and declining, this patient's β-hCG of 3,200 is too high for expectant management alone. Medical management is more reliable. | | Dilation and curettage | D&C is contraindicated in suspected ectopic pregnancy. It will not treat the ectopic and risks uterine perforation and hemorrhage. Transvaginal ultrasound has already ruled out intrauterine pregnancy. | ## Management Algorithm for Unruptured Ectopic ```mermaid flowchart TD A[Unruptured Ectopic Pregnancy]:::outcome --> B{Hemodynamically Stable?}:::decision B -->|No| C[Laparoscopy/Laparotomy]:::urgent B -->|Yes| D{β-hCG Level?}:::decision D -->|< 1000| E{Declining β-hCG?}:::decision D -->|1000-5000| F[Single-Dose Methotrexate]:::action D -->|> 5000| G[Laparoscopic Salpingostomy]:::action E -->|Yes| H[Expectant Management]:::action E -->|No| F F --> I[Serial β-hCG Days 4, 7, 14]:::action I --> J{β-hCG Declining ≥15%?}:::decision J -->|Yes| K[Continue Monitoring]:::action J -->|No| L[Repeat MTX or Surgery]:::action ``` **Mnemonic:** **STABLE ECTOPIC** = Suitable for medical management - **S**table hemodynamics - **T**ube unruptured - **A**dnexa mass <3.5 cm - **B**-hCG <5,000 (ideally <3,000) - **L**ow risk (no cardiac activity) - **E**ligible for follow-up - **E**xpectant or medical option preferred - **C**ontraindications to MTX absent - **T**rusting patient compliance - **O**ptions discussed (shared decision-making) - **P**roven efficacy (88–96% success) - **I**ntramuscular single-dose preferred - **C**lose monitoring mandatory