In Pearl index formula, Pregnancy rate per HWY:
The use-effectiveness of contraceptive method is expressed as Pearl rate & life table technique. Pearl rate or pearl index was introduced by Raymond Pearl in 1932 The rate is expressed as pregnancy rate per 100 women years (HWY) & calculated as Pregnancy rate per HWY = Total accidental pregnancies x 1200/ Number of women observed x Total months of use of contraceptive 1200 is the number of months in 100 years
Total accidental pregnancies x 1200 / Number of women observed x Total months of use of contraceptive
Total months of exposure to unintended pregnancy X 1200 / Accidental pregnancies
Total accidental pregnancies x 100 / Number of women Total months of exposure to unintended pregnancy
Total accidental pregnancies / Total months of exposure to unintended pregnancy
Contraceptives