A 24-year-old unmarried woman presents to the emergency department 18 hours after unprotected intercourse. She is anxious and requests emergency contraception. Her last menstrual period was 10 days ago. She has no contraindications to hormonal therapy. What is the most appropriate next step in management?

Explanation

## Emergency Contraception: Timing and First-Line Management **Key Point:** Levonorgestrel (Plan B) is the most effective and accessible emergency contraceptive when given within 72 hours of unprotected intercourse, with efficacy decreasing with time. ### Timing Window for Levonorgestrel - **Optimal window:** Within 72 hours of intercourse - **This patient:** 18 hours post-intercourse — well within the window - **Efficacy:** ~60% if given within 24 hours; ~40% by 72 hours - **Mechanism:** Primarily prevents or delays ovulation; does NOT disrupt established pregnancy **High-Yield:** Levonorgestrel is **NOT effective if ovulation has already occurred**. Since the patient is on day 10 of her cycle (ovulation typically occurs day 14), she is in the pre-ovulatory window—ideal timing for levonorgestrel. ### Why Levonorgestrel Now? 1. **No need for pregnancy test beforehand** — levonorgestrel does not harm an established pregnancy (though pregnancy is extremely unlikely at 18 hours post-intercourse) 2. **Immediate administration is crucial** — efficacy decreases with every passing hour 3. **Oral, accessible, no contraindications noted** — patient has no listed medical barriers ### Comparison: Emergency Contraceptive Options | Method | Timing Window | Efficacy | Mechanism | Notes | |--------|---------------|----------|-----------|-------| | Levonorgestrel (Plan B) | ≤72 hours | 60–40% | Ovulation inhibition | First-line, OTC available | | Ulipristal acetate (ella) | ≤120 hours | 65–45% | Selective progesterone receptor modulator | More effective in days 3–5; prescription | | Cu-IUD | ≤5 days | >99% | Spermicide + inflammatory effect | Gold standard if no contraindications; invasive | | Mifepristone | ≤72 hours | ~95% | Progesterone antagonist | Not available in many countries; abortion agent | **Clinical Pearl:** The copper IUD is actually MORE effective than levonorgestrel (>99% vs. 60%) but requires insertion by a trained provider and is more invasive. It is reserved for women who present within 5 days and have no contraindications (e.g., PID, STI, anatomical abnormality). ### Why Not the Other Options? **Pregnancy test first (Option B):** Unnecessary delay. At 18 hours post-intercourse, pregnancy is virtually impossible to detect (hCG not yet detectable). Delaying levonorgestrel administration reduces efficacy. **Cu-IUD insertion (Option C):** While highly effective, it is more invasive and requires a trained provider. Levonorgestrel is the first-line, non-invasive option for this patient who presents well within 72 hours. Cu-IUD is preferred in women presenting 3–5 days post-intercourse or those with repeated unprotected intercourse in a cycle. **Observation alone (Option D):** Unacceptable. Emergency contraception is indicated and should be offered immediately. Waiting increases the risk of unintended pregnancy.