This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Demography and Family Planning, Subject name: Social & Preventive Medicine
[{'content': 'Contraceptive efficacy measured by - \nSelect and explain. \nA. Pearl index, B. CPR, C. BBT method, D. Cervical mucous method', 'role': 'user'}, {'content': 'Answer: A \nExplanation: (A) (Pearl index) (471 - Park 22nd)Pearl index and life table analysis** are used to measure contraceptive efficacy(A) PEARL INDEX is defined as the number of failures per 100 woman - years of exposure (HWY)Failure rate per HWY =Total accidental pregnancies------------------Total months of exposurex 1200* The factor 1200 is the number of months in 100 years*** Total month of exposure in the denominator is obtained by deducting from period under review of 10 months for a full term pregnancy and 4 months for an abortion.* Pearl index limitation is over come by using the method life-table analysis***(B Life-Table Analysis:* Calculative failure rate for each months of use*** A cumulative failure rate can then compare methods for any specific length of exposure.* Women who leave a study for any reason other than unintended pregnancy are removed from the analysis contributing their exposure until the time of the exit.', 'role': 'assistant'}]