How effective is Natural Cycles as a contraceptive?

When it comes to efficacy, the main method for calculating is it the Pearl Index, which we have done in two clinical studies on the efficacy of Natural Cycles used as contraception.

The pearl index is the most commonly used indicator of how effective a contraceptive method is. It typically shows how many women get pregnant during one year of applying a contraceptive. This indicator can be calculated in various ways, which is explained below. So this is a great way for you to compare contraceptives to each other and choose which one is best for you. While keeping effectiveness in mind you should also consider possible side effects and how it is used.

Method failure rate of 0.5, which is a measurement of how often the app incorrectly displays a green day when the woman is actually fertile, and she gets pregnant after having unprotected intercourse on this green day. This means that 5 out of 1,000 women who use the app for one year will become pregnant due to a falsely attributed green day.

Perfect use failure rate of 1.0, which means that 10 out of 1000 women who use the app for one year and who become pregnant will do so either because: 
a. They had unprotected intercourse on a green day that was falsely attributed as non-fertile (i.e., method failure);
b. They had protected intercourse on a red day, but the chosen method of contraception failed.

Typical use failure rate of 6.8, which means that in total 68 women out of 1000 get pregnant during one year of use due to all possible reasons (e.g. wrong attributed green days, having unprotected intercourse on red days and failure of the contraceptive method used on red days).

Having studied over 22’785 women, who were 29 years of age on average, and analysed 224'563 menstrual cycles this is the largest prospective study carried out not only on Natural 
Cycles, but on natural contraception as of yet. It demonstrates the efficacy of Natural Cycles as a method of contraception by analysing women’s real-life data. 

Be sure to refer to the instructions for use to ensure you are using Natural Cycles correctly.