Which of the following statements about the Pearl Index is correct in the context of contraceptive efficacy evaluation?

Explanation

## Pearl Index in Contraceptive Epidemiology **Key Point:** The Pearl Index is a classical measure of contraceptive failure that expresses failure rate as the number of unintended pregnancies per 100 woman-years of exposure. ### Pearl Index Formula $$\text{Pearl Index} = \frac{\text{Number of unintended pregnancies} \times 1200}{\text{Total number of months of exposure}}$$ Or equivalently: $$\text{Pearl Index} = \frac{\text{Number of unintended pregnancies} \times 100}{\text{Total number of woman-years of exposure}}$$ ### Comparison of Failure Rate Methods | Method | Unit | Strengths | Limitations | |---|---|---|---| | **Pearl Index** | Failures per 100 woman-years | Simple calculation; historically standard | Does not account for dropouts; biased if losses are non-random | | **Life-table method** | Cumulative probability over time | Accounts for dropouts and losses | More complex; requires longer follow-up | | **Kaplan-Meier** | Survival curve | Handles censoring properly; best for LARCs | Requires statistical software | **High-Yield:** The Pearl Index is the most commonly cited measure in older literature and Indian textbooks, but it is **not ideal** for LARCs because it does not account for loss to follow-up. **Clinical Pearl:** Modern contraceptive trials increasingly use life-table or Kaplan-Meier methods, especially for IUDs and implants, because these methods properly handle women who drop out or are lost to follow-up. **Mnemonic:** **Pearl = Per 100 woman-years** (simple, historical, but flawed for dropouts).