<prompt> Pearls indexPer 10 woman yearsPer 100 woman yearsPer 1000 woman yearsPer 10,000 woman years  <response>: Pearl index is defined as the number of failures per 100 woman years of exposure HWY Failure rate per Hundred Women Years Total accidental pregnancies X 1200 Total months of exposure Reference : Park;s textbook of preventive and social medicine, 23rd edition, Page no: 510 