What is Natural Cycles?
In August 2018, Natural Cycles became the first smartphone application (“app”) for contraception cleared by the FDA. Natural Cycles is a high-tech version of the classic rhythm method (also called natural family planning or the fertility awareness method) in which users track their ovulation cycles in order to avoid pregnancy. It is one of several dozen fertility apps available for download in the US that uses personal health information uploaded by users to predict days on which it is and isn’t safe to have unprotected sex.
To learn more about how the app works—and why it might not be a good choice for most people—visit our health information fact sheet.
What Makes Natural Cycles an FDA-Cleared Contraceptive?
The company boasts that the accuracy of its algorithm makes it as effective as the birth control pill. But is it? We don’t think so, and we question the FDA’s decision to rush the app through the clearance process.
When a new medical device is seeking FDA approval but no similar device has already been approved, the FDA automatically designates it as a Class III device—the highest risk category, which includes pacemakers and replacement heart valves. Before they’re allowed on the market, Class III devices are subject to a rigorous premarket approval process (PMA) that can take years to complete. First-of-a-kind devices are typically reviewed by an advisory committee of experts. The committee must hold a public meeting and submit a final report that includes their recommendation and an overview of the evidence they considered.
Congress created the de novo process to give low-risk products a faster path to clearance even if they're the first of their kind. Despite the risks posed by contraceptive failure, the FDA allowed Natural Cycles to use the expedited de novo process, and does not appear to have held the device to the same high standards that it requires of other contraceptive methods. For example, Annovera, a new vaginal ring system approved on the same day, underwent an extensive review process before approval. The FDA also allowed Natural Cycles to skip a public advisory committee review that might have raised red flags about the quality of the data submitted by the company.
Traditional fertility awareness methods have a “typical use” failure rate of 24%—meaning, out of every 100 people using the method, 24 will become pregnant in a year. In contrast, Natural Cycle’s developers claim that the app has a “typical use” failure rate of 6.5%, slightly better than hormonal contraceptives like the pill, patch, and vaginal ring. The NWHN is concerned that FDA scientists did not adequately examine the data used to come up with this rate and that the studies conducted by the company do not represent the experiences of a typical contraceptive user.
In order to determine their 6.5% failure rate, Natural Cycles used real-world data from their users. The data likely do not represent the experiences of the average contraceptive user and may not even represent many of the people who try the app before ultimately quitting. One medical expert cautioned that “there is a significant amount of missing data, and drop-out rates are quite high. The study was not designed according to the standards of an efficacy trial, so it seems inappropriate and misleading to offer this claim.”
"On the pill, it didn’t matter if I’d just woken up, was lying down or standing up when I took it. With Natural Cycles, the slightest motion seemed to count. It was comedic until it became tragic; I got pregnant when the predictions of fertile and infertile changed back and forth in one day, turning from green to red, after I had unprotected sex."
- Olivia Sudjic, The Guardian
When pressed, the company seemed to acknowledge these limitations. Calling them “highly motivated,” Natural Cycles chief executive described their users as “age 30 on average, in a stable relationship with a regular daily routine, and willing to take their temperature on a daily basis and use protection on fertile days.”
Yet the company’s aggressive marketing campaigns target contraceptive users among the general public with the idea that the pill and the app are comparable. Many of these users are likely to find that correctly using the app is more difficult than correctly using hormonal contraceptives such as the pill.
All of this suggests that the effectiveness of the app is almost certainly overestimated for the general public. And in fact, the FDA itself warns that “Natural Cycles should not be used by women who have a medical condition where pregnancy would be associated with a significant risk to the mother or the fetus.” Annovera, the new vaginal ring approved on the same day, has a similar typical use failure rate but did not carry this same warning, suggesting that even the FDA may believe the app’s real failure rate is higher. But by accepting Natural Cycles’ claims uncritically, the FDA is allowing the company to promote a potentially false effectiveness rate with the agency’s stamp of approval.