Failure rate of contraceptive method is determined by-

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.