Natural Cycles, a mobile phone application that can be used to prevent pregnancy, was cleared by the Food and Drug Administration on Friday for direct-to-consumer marketing in the U.S. The app has been described as "digital contraception" by its maker, the privately-held, Sweden-based NaturalCycles Nordic AB. It uses temperature readings from a basal body thermometer to track a woman's menstrual cycle, as minor temperature rises occur around the time of ovulation. The app tells women when they are fertile, and they should avoid sex or use contraception during that time, according to the FDA. That strategy is an old one, sometimes called "natural family planning" or "the rhythm method," but Natural Cycles says its special approach, which uses a "smart algorithm," is highly effective. According to the FDA, clinical studies involving about 15,600 women found that when used perfectly, the failure rate - meaning women getting pregnant - was 1.8%, while with typical use, or women sometimes not using the app correctly, the failure rate was 6.5%. Women in the study used the app for an average of eight months. By way of comparison, condoms have a perfect use failure rate of 2% and a typical use failure rate of 18%; for IUDs, typical and perfect use failure rates are all below 1%. The FDA compared Natural Cycles' effectiveness to that of any other contraceptive, with Terri Cornelison, assistant director for the health of women in the FDA's Center for Devices and Radiological Health, noting that "no form of contraception works perfectly, so an unplanned pregnancy could still result from correct usage of this device." But a number of alarms have been raised about the app resulting in unintended pregnancies, including in a recent Guardian report whose author reported getting pregnant while using the app. Natural Cycles requires users input temperature data into the app, making it, like other forms of contraception, highly prone to human error. And, importantly, the app cannot warn when ovulation begins early -- and when ovulation occurs in the month is highly unpredictable, according to a Wired report from earlier this year. The FDA says the app shouldn't be used by individuals for whom pregnancy would be a major risk to the mother or fetus, nor by women who are using contraception that inhibits ovulation. Natural Cycles was cleared through a FDA pathway for new types of low-to-moderate risk devices, and controls have been put in place to "provide a reasonable assurance of safety and effectiveness," according to the regulator. Other products like Natural Cycles may be able to get the same marketing authorization from the FDA by showing they are substantially similar to it. Natural Cycles was certified as a method of contraception in the European Union last year.
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