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 110/70, HR 82). Serum β-hCG is 3200 mIU/mL. Transvaginal ultrasound shows an empty uterus, no free fluid, and a 2.5 cm gestational sac-like structure in the left adnexa with no fetal heart activity. What is the most appropriate next step in management?

Explanation

## Clinical Diagnosis This patient has an **unruptured, haemodynamically stable ectopic pregnancy** suitable for **medical management** with methotrexate. ### Key Clinical Features Supporting Medical Management - **Haemodynamic stability:** BP 110/70, HR 82 (normal) - **No rupture signs:** No free fluid, no peritoneal irritation - **β-hCG level:** 3200 mIU/mL (ideal for methotrexate: <5000) - **No fetal cardiac activity:** Confirms non-viable pregnancy - **Adnexal mass:** 2.5 cm (suitable for medical therapy) **Key Point:** Methotrexate is the first-line medical treatment for unruptured, haemodynamically stable ectopic pregnancies with β-hCG <5000 and no contraindications. ## Management Decision Tree ```mermaid flowchart TD A[Confirmed Ectopic Pregnancy]:::outcome --> B{Haemodynamically stable?}:::decision B -->|No| C[Emergency Laparotomy]:::urgent B -->|Yes| D{β-hCG level?}:::decision D -->|>5000 or contraindications| E[Surgical: Laparoscopy ± Salpingectomy]:::action D -->|<5000 + stable + no CI| F[Medical: Methotrexate]:::action F --> G[Single-dose IM 50 mg/m²]:::action G --> H[Serial β-hCG: days 4 & 7]:::action H --> I{β-hCG decline >15%?}:::decision I -->|Yes| J[Weekly β-hCG until negative]:::action I -->|No| K[Consider 2nd dose or surgery]:::action ``` ## Methotrexate Protocol (Single-Dose Regimen) | Parameter | Details | |-----------|----------| | **Dose** | 50 mg/m² IM (or 1 mg/kg) | | **Timing** | Single intramuscular injection | | **β-hCG monitoring** | Days 4 & 7 post-injection | | **Success criterion** | ≥15% decline in β-hCG between days 4 & 7 | | **Follow-up** | Weekly β-hCG until undetectable | | **Success rate** | 88–96% with β-hCG <5000 | | **Contraindications** | Immunodeficiency, blood dyscrasias, renal/hepatic disease, active pulmonary disease, peptic ulcer | **High-Yield:** Methotrexate is a **folate antagonist** that inhibits dihydrofolate reductase, blocking DNA synthesis in rapidly dividing trophoblastic cells. It is **not** an abortifacient — it arrests growth of the ectopic pregnancy, allowing resorption. **Clinical Pearl:** The **15% decline rule** on days 4–7 predicts success. If decline is <15%, a second dose or surgical intervention is needed. ## Why This Patient Qualifies for Medical Management 1. **Haemodynamically stable** — no shock, no peritoneal signs 2. **β-hCG <5000** — optimal for methotrexate efficacy 3. **No rupture** — no free fluid on ultrasound 4. **No fetal cardiac activity** — confirms non-viability 5. **No contraindications mentioned** — no renal, hepatic, or haematologic disease **Mnemonic: STABLE** — **S**table vitals, **T**rophoblast <5000, **A**dnexa <3.5 cm, **B**lood-free, **L**ow risk, **E**ligible for medical Rx. [cite:Jeffcoate's Principles of Gynaecology 15e Ch 11; RCOG Green-top Guideline 21]