A 32-year-old woman presents 5 days after unprotected intercourse requesting emergency contraception. She has taken levonorgestrel 1.5 mg as a single dose 2 days ago but is now reporting persistent lower abdominal pain and vaginal bleeding. Which investigation is most appropriate to assess the current status?

Explanation

## Investigation of Choice for Post-EC Complications Assessment ### Clinical Scenario The patient has taken levonorgestrel within the recommended window (5 days post-intercourse) but is now presenting with: - Persistent lower abdominal pain - Vaginal bleeding These symptoms raise concern for: 1. **Ectopic pregnancy** (if EC failed) 2. **Intrauterine pregnancy** (if EC failed) 3. **Spontaneous abortion** (if pregnancy occurred and is terminating) 4. **Hemorrhagic corpus luteum cyst** (rare, but possible with hormonal EC) ### Why Serum β-hCG and Transvaginal Ultrasound is the Investigation of Choice **Key Point:** When a woman on EC presents with abdominal pain and bleeding, the first priority is to determine pregnancy status and localize the pregnancy (intrauterine vs. ectopic). **High-Yield:** - **Serum β-hCG:** Quantifies hCG level to confirm pregnancy and assess trend (rising, stable, or falling) - Rising hCG → viable intrauterine or ectopic pregnancy - Falling hCG → spontaneous abortion or resolving pregnancy - Negative hCG → EC was successful; symptoms likely due to other cause (e.g., corpus luteum cyst, PID) - **Transvaginal ultrasound:** Gold standard for localizing pregnancy - Confirms intrauterine gestational sac (if hCG positive) - Rules out ectopic pregnancy - Assesses viability (fetal heart rate, crown-rump length) - Evaluates for other pelvic pathology (cysts, free fluid, signs of infection) **Clinical Pearl:** Ectopic pregnancy is a medical emergency. Even though EC has a low failure rate (~1–3%), it does NOT prevent ectopic pregnancy. Any woman on EC presenting with abdominal pain, bleeding, and positive hCG must be evaluated urgently for ectopic pregnancy. ### Diagnostic Algorithm ```mermaid flowchart TD A[Woman on EC with abdominal pain + bleeding]:::outcome --> B[Serum β-hCG]:::action B --> C{hCG positive?}:::decision C -->|Yes| D[Transvaginal ultrasound]:::action D --> E{Intrauterine gestational sac?}:::decision E -->|Yes| F[Viable IUP or threatened abortion]:::outcome E -->|No| G[Ectopic pregnancy until proven otherwise]:::urgent C -->|No| H[EC successful; evaluate for other causes]:::outcome H --> I[Corpus luteum cyst, PID, or other pathology]:::outcome ``` ### EC Failure and Ectopic Risk - EC failure rate: 1–3% (varies by method and timing) - EC does NOT prevent ectopic pregnancy - If pregnancy occurs despite EC, ectopic pregnancy risk is proportionally higher among failures **Mnemonic: BEAT** — Before Evaluating Abdominal pain in EC users, Think: - **B**eta-hCG (quantitative) - **E**xtension (intrauterine vs. ectopic) - **A**ssess viability - **T**ransvaginal ultrasound (gold standard) [cite:Park 26e Ch 9; Harrison 21e Ch 297]