## Pearl Index and Contraceptive Efficacy **Key Point:** The Pearl Index (number of unintended pregnancies per 100 woman-years of use) is the standard epidemiological measure of contraceptive failure in India and globally. ### Comparative Pearl Index Values | Contraceptive Method | Pearl Index (failures/100 woman-years) | Type | |---|---|---| | LNG-IUD (Mirena) | 0.2–0.5 | Long-acting reversible | | Copper T 380A | 0.6–0.8 | Long-acting reversible | | Combined oral pills (typical use) | 8–9 | Short-acting | | Barrier methods + spermicide | 15–20 | Short-acting | | Male sterilization | 0.1–0.15 | Permanent | | Female sterilization | 0.5–1.0 | Permanent | **High-Yield:** Among *reversible* methods, the **LNG-IUD (levonorgestrel-releasing intrauterine device)** has the lowest failure rate due to: - Direct intrauterine hormone release - Thickening of cervical mucus - Suppression of ovulation in some cycles - No user-dependent compliance issues **Clinical Pearl:** Although copper T 380A is highly effective and more widely available in India, the LNG-IUD is superior in efficacy. However, copper T remains the first-line LARC in resource-limited settings due to cost and availability. **Warning:** Do not confuse Pearl Index with *perfect use* vs. *typical use* failure rates. The Pearl Index typically reflects typical-use data (real-world compliance). [cite:Park 26e Ch 6]
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