If a woman experiences 2.5 accidental pregnancies after using a contraceptive method, Pearl index:
D i.e. 10 accidental pregnancies per 100 women years using contraceptivesRef: Park, 24th edition, page 544; Principles and Practice of Community Medicine by DrAsma Rahim, 2nd edition, page 439ExplanationPearl index = (Total accidental pregnancies/total months of exposure) * 1200 = * 1200 = 10 per 100 woman years25 years is considered as the average fertile period for a woman for calculation.Contraceptive EffectivenessAssessed by measuring the number of unplanned pregnancies that occur during a specified period of exposure and use of contraceptive method. Two methods are used:Pearl index.Life table analysis.The numerator "total accidental pregnancies" includes all unwanted pregnancies irrespective of the outcome, i.e.,Livebirth.Abortion.Stillbirth; orStill not terminated.DisadvantagesA minimum of 600 months of exposure is necessary for obtaining a valid "failure rate" value.Life table analysis:Calculates failure rate per month of use.More precise than Pearl Index.
0.1 per 100 woman years
100 per 1000 woman years
10 accidental pregnancies per 1000 woman years using contraceptives
10 accidental pregnancies per 100 woman years using contraceptives
Demography and Family Planning