Hmm, not sure how badminton balls and turquoise rocks factor into the contraceptive process.
Image: Natural Cycles

On Friday, the Food and Drug Administration gave marketing approval to Natural Cycles, an app that dubs itself “digital birth control.” It’s the first time a fertility-tracking app has gotten the official OK to advertise itself as birth control, which might seem an exciting leap into the baby-preventing future of our wildest hopes and dreams. Reliable contraception without pills or hormones!

But, as Vice points out, the app has been blamed for dozens of unintended pregnancies and is being investigated in Sweden and the United Kingdom.

Natural Cycles, which costs $79.99 for a year, relies on women taking their temperature every morning using a basal body thermometer, which can detect the minor temperature changes that happen around ovulation. That information is entered into the app, which uses an algorithm to predict when users are more likely to be fertile—and, on those days, it tells them to “use protection.”

There is evidence to suggest that this approach can work. Natural Cycles was tested in clinical studies with over 15,000 women, as the FDA reports in a press release. When used exactly as instructed, the app had a 1.8 percent failure rate (meaning nearly two women out of 100 who use the app for a year will become pregnant). But under “typical use”—which is, you know, how people actually tend to use it—the failure rate rose to 6.5 percent.

For comparison, the pill has a nine percent “typical use” failure rate, and the IUD has one of less than one percent, according to the Centers for Disease Control and Prevention.

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Still, the potential for unintended pregnancies with Natural Cycles has sparked concern. Earlier this year, the Verge reported that a Swedish hospital recorded 37 cases of unintended pregnancies among women using Natural Cycles and, as Vice notes, medical authorities are currently investigating the app. In the U.K., advertising authorities have launched an investigation into Natural Cycles’ Facebook ads, which call the app “highly accurate.”

The FDA wouldn’t comment to Vice on the U.K. advertising investigation, but did address the Swedish case. “An increase in the absolute numbers of unintended pregnancies is expected with a growing number of users,” said spokesperson Deborah Kotz. “We reached out to the Swedish authorities and feel that the information regarding the pregnancies in Sweden is consistent with our knowledge concerning the pregnancy risks associated with use of this device.”

In the FDA’s press release, it claims that Natural Cycles “can provide an effective method of contraception if it’s used carefully and correctly,” but goes on to say that “women should know that no form of contraception works perfectly, so an unplanned pregnancy could still result from correct usage of this device.”