Pearls index: (A) Per 10 woman years, (B) Per 100 woman years, (C) Per 1000 woman years, (D) Per 10,000 woman years
Answer is B. 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