A 28-year-old woman presents to the emergency department 18 hours after unprotected intercourse during her fertile window. She has no contraindications to any form of emergency contraception. Her last menstrual period was 12 days ago, and her cycle is regular (28 days). She is anxious about pregnancy and requests the most effective emergency contraceptive option available. What is the best recommendation?

Explanation

## Emergency Contraception: Efficacy Hierarchy **Key Point:** The copper IUD is the most effective emergency contraceptive method, with efficacy >99% when inserted within 5 days of unprotected intercourse, and remains effective up to 10 days if ovulation has not yet occurred. ### Comparative Efficacy | Method | Efficacy | Timing | Mechanism | |--------|----------|--------|----------| | Copper IUD | >99% | Within 5 days (up to 10 if pre-ovulatory) | Spermicidal, endometrial inflammation | | Mifepristone 10 mg | 98–99% | Within 72 hours (some data to 120 hours) | Progesterone antagonist; delays/prevents ovulation | | Levonorgestrel 1.5 mg | 60–90% | Within 72 hours (less effective >72 hrs) | Delays ovulation; less effective in luteal phase | | Yuzpe regimen | 50–80% | Within 72 hours | Estrogen + progestin; delays ovulation | **High-Yield:** In this case, the patient is at 18 hours post-coitus and is in the fertile window (cycle day 12 of 28). The copper IUD is the single most effective option and should be offered first if there are no contraindications (pregnancy, active infection, anatomical distortion). ### Why Copper IUD Is Superior 1. **Highest efficacy:** >99% vs. 60–90% for levonorgestrel 2. **Longer window:** Effective up to 5 days (and up to 10 days if pre-ovulatory) 3. **Dual benefit:** Acts as both emergency contraceptive AND long-acting reversible contraception (LARC) for future protection 4. **Mechanism:** Creates hostile endometrial environment; spermicidal effect; may prevent implantation **Clinical Pearl:** Mifepristone (a progesterone antagonist) is more effective than levonorgestrel, especially in the luteal phase, but is not widely available in India and is subject to regulatory restrictions. Levonorgestrel loses efficacy significantly after 72 hours and is less effective in the luteal phase (when progesterone levels are rising). **Mnemonic:** **CUD** = **C**opper **U**terine **D**evice — the gold standard for EC. [cite:Park 26e Ch 9]