Natural Cycle’s 100,000 users currently input their daily basal body temperature — they can take these measurements precisely using the company’s basal thermometer, which can be calibrated through the app. These data points are compared against Natural Cycle’s datasets to determine users’ fertility (during ovulation, women’s body temperatures rise up to 0.45 degree Celsius).
When it’s safe for users to have sex without the risk of pregnancy, the app shows a green day in its calendar interface. When they will need to use a condom or another form of contraception to prevent pregnancy, the day will show as red.
Natural Cycles’s algorithm was developed by co-founder Elina Berglund, who was part of the team at CERN (the European Organization for Nuclear Research) that helped discover the Higgs boson particle. “I wanted to give my body a break from the pill,” she told Wired, “but I couldn’t find any good forms of natural birth control, so I wrote an algorithm for myself.”
And it looks as though that algorithm really works. In conducting their tests, Tüv Süd found that over the course of a year, 143 unplanned pregnancies occurred, but only 10 occurred on green days. That gave Natural Cycles a 99.5 percent efficacy rating, which is the same as the pill. An efficacy rating, however, is not the same as being 99.5 percent effective.
Co-founder Raoul Scherwitzl also noted to Wired that the firm is already discussing making Natural Cycles free as well (as it stands, users pay 7 pounds a month (just under $9).
While this approval is a huge step forward for the app, which has recently been updated along with a redesigned website, experts warn that Natural Cycles should still be taken with a grain of salt (or perhaps with another form of contraception). “Natural Cycles is not recommended to those who are very young or very keen to avoid a pregnancy since there are other more effective methods,” said Kristina Gemzell Danielsson, from Swedish medical institute Karolinska Institutet. “The efficacy is far below that of intrauterine contraception or implants, but similar to that of the pill when used in real life.”
To learn more about Natural Cycles and its approval, check out the full blog post here.
