Question:medium
Out of 100 women offered oral contraceptive pills (OCP) for contraception, 10 women became pregnant when followed for 24 months. What is the Pearl index?
Out of 100 women offered oral contraceptive pills (OCP) for contraception, 10 women became pregnant when followed for 24 months. What is the Pearl index?
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Pearl index = (pregnancies x 1200) / total woman-months.
Updated On: Jun 24, 2026
- 10
- 5
- 4
- 2
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The Correct Option is B
Solution and Explanation
Step 1: The Pearl index expresses how often a contraceptive method fails, scaled to 100 women using it for one year (100 woman-years).
Step 2: It is computed as $\dfrac{\text{pregnancies} \times 1200}{\text{woman-months of use}}$, the 1200 coming from 100 women followed for 12 months.
Step 3: With 10 pregnancies over 100 women followed for 24 months, the total exposure is $100 \times 24 = 2400$ woman-months, so \[\frac{10 \times 1200}{2400} = 5.\]
Step 4: The failure rate therefore works out to 5 pregnancies per 100 woman-years. \[\boxed{5}\]
Step 2: It is computed as $\dfrac{\text{pregnancies} \times 1200}{\text{woman-months of use}}$, the 1200 coming from 100 women followed for 12 months.
Step 3: With 10 pregnancies over 100 women followed for 24 months, the total exposure is $100 \times 24 = 2400$ woman-months, so \[\frac{10 \times 1200}{2400} = 5.\]
Step 4: The failure rate therefore works out to 5 pregnancies per 100 woman-years. \[\boxed{5}\]
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