This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
[{'content': 'Failure rate of contraceptive method is determined by- \nSelect and explain. \nA. Pearl index, B. Half 1 ife, C. Number of accidental pregnancies, D. Period of contraceptive practice continued', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e., Pearl index Pearl index o Contraceptive methods are evaluated by Pearl index Pearl index is "failure rate per hundred women years of exposure (HWY)" Failure rate per HWY -- Total accidental pregnancies x 1200 Total months of exposure o In applying the above formula, the total accidental pregnancies shown in the numerator, must include every known conception, whatever its outcome. The factor 1200 is the number of months in 100 yrs. o A failure rate of 10 per HWY would mean that in the lifetime of an average women about one fouh or 2.5 accidental pregnancies would result, since the average feile period of a women is about 25 yrs.', 'role': 'assistant'}]