The second clinical study on Natural Cycles showed that 7 women out of 100 got pregnant in 1 year (equivalent to a typical use Pearl Index of 7.0) when using Natural Cycles. Our CE mark is based on mandatory clinical evidence that demonstrates a 93% typical use effectiveness rate in more than 22,000 women (1).
For the FDA clearance, an additional clinical study of more than 15,000 women was carried out. In this prospective study, Natural Cycles demonstrated a typical use Pearl Index of 6.5. This means that on average, 6.5 women out of 100 women get pregnant during one year of use with Natural Cycles, which equals a 93% effectiveness rate (rounded up).
The typical use Pearl Index refers to how many women get pregnant using Natural Cycles in general, also taking into account incidents of the method used on red days failing (e.g. condom breaks) or human error (having unprotected sex on a red day) whereas method failure rate refers to the app attributing a false green day within the fertile window.
Be sure to refer to the instructions for use to ensure you are using Natural Cycles correctly.
(1) Berglund Scherwitzl E, et al. Contraception. 2017;96(6):420–425.