Contraceptive efficacy of the personal hormone monitoring system Persona.
Since this new algorithm, used in the Persona system, is based on flawed logic, the annual risk of pregnancy is actually higher than the estimated 6% among women using Persona and having intercourse in each cycle except on red days.
Abstract
This is a commentary on the contraceptive effectiveness of the personal hormone-monitoring system Persona; it points out the various errors committed in computing method pregnancy rates. The modifications presented by Bonnar et al. on the incorrect procedure for computing method pregnancy rates are criticized as erroneous because the denominator includes cycles in which there is no risk of a method pregnancy according to the authors' algorithm for classifying pregnancy in an imperfect-use cycle. It is also claimed that the new exercise is a more complicated and less accurate way of computing for pregnancy rates by comparison with the simpler alternative. Since this new algorithm, used in the Persona system, is based on flawed logic, the annual risk of pregnancy is actually higher than the estimated 6% among women using Persona and having intercourse in each cycle except on red days.