## Pearl Index and Contraceptive Efficacy **Key Point:** The Pearl Index measures contraceptive failure rate as the number of unintended pregnancies per 100 woman-years of use. Lower Pearl Index = higher efficacy. ### Comparative Pearl Index Values | Contraceptive Method | Pearl Index (failures/100 woman-years) | |---|---| | Copper IUD (T 380A) | 0.8–1.0 | | LNG-IUS (Mirena) | 0.1–0.2 | | Combined oral pills | 3–5 | | Barrier methods | 10–15 | | Lactational amenorrhea | 2–5 | | Fertility awareness | 10–20 | **High-Yield:** Among reversible methods, **intrauterine devices (both copper and hormonal) have the lowest Pearl Index**, making them the most effective reversible contraceptives available. The copper T 380A has a Pearl Index of 0.8–1.0, approaching that of sterilization. **Clinical Pearl:** IUDs are classified as **"set and forget"** methods because they require minimal user compliance once inserted, contributing to their superior real-world efficacy compared to user-dependent methods like pills or barriers. **Mnemonic:** **LARC > SARC** — Long-Acting Reversible Contraceptives (IUDs, implants) outperform Short-Acting Reversible Contraceptives (pills, barriers) in efficacy due to lower user-dependent failure. ### Why IUD Efficacy Is Superior 1. **No user compliance required** after insertion (unlike pills or condoms) 2. **Continuous action** for 5–10 years (copper) or 3–5 years (hormonal) 3. **Mechanism independent of coitus** (unlike barrier methods) 4. **Reversible** (unlike sterilization) but with efficacy approaching permanent methods [cite:Park 26e Ch 8]
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