T

he FDA on Friday cleared the first-ever app to prevent pregnancy — but not everyone is convinced it works.

The app, Natural Cycles, isn’t your typical form of contraception. It asks women to take their temperature upon waking and keep a daily log in its interface. It uses that data to help women keep track of when they’re ovulating. 

The FDA cleared the app as a medical device, using a regulatory pathway reserved for low-to-moderate risk devices. 

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According to the FDA’s press release, the app’s typical-use failure rate was about 6.5 percent in large-scale clinical trials — far better than the reported 24 percent typical failure rate of “fertility awareness,” commonly known as the “rhythm method.”

The typical-use failure rate of the birth control pill is about 9 percent, according to the CDC. A hormonal IUD has a failure rate of less than 1 percent, while condoms alone have a typical-use failure rate of 18 percent.

“Consumers are increasingly using digital health technologies to inform their everyday health decisions, and this new app can provide an effective method of contraception if it’s used carefully and correctly,” Terri Cornelison, the assistant director for the health of women in the FDA’s Center for Devices and Radiological Health, stated in a press release.

Natural Cycles got European clearance in February 2017. But in January, the Swedish Medical Products Agency announced it was investigating the app after reports that 37 women in one Swedish clinic who were using the app had become pregnant accidentally. One woman wrote about her own experiences in The Guardian in July.

Some people have expressed concerns via social media that basal temperature, estimated by taking the measurement immediately after waking, may be an unreliable metric to use.

Dr. Juan Acuna, an OB-GYN specialist at Florida International University and one of Natural Cycle’s scientific advisers, said “the whole realm of natural contraception has always been deemed as not being one of the safest.”

Monitoring ovulation properly relies on multiple measurements over a long time — and even then, stress and other factors affect the data. The app, he said, makes otherwise difficult calculations simpler. All forms of birth control come with at least a small risk of failure. “During the first two or three or four months, you need to use two methods,” he said.

And even Acuna noted that basal temperature isn’t the best possible way to predict fertility. “The gold standard [to measure ovulation] is ultrasound,” Acuna noted. “It might not be the safest form of data, but when you balance the pros and cons, all in all, of doing other tests and the cumbersome process of measuring cervical mucus characteristics, then body temperature is still a good measurement to take.”

This app’s clearance also means that future contraceptive apps will be able to go through a different, simpler process — albeit with some special considerations. Now that one app is on the market, any other app that is substantially similar will be able to go through the FDA’s 510(k) medical device marketing notification procedure. But they must meet the agency’s new “special controls” — criteria that the agency says will “provide a reasonable assurance of safety and effectiveness for apps used for contraception.”

The FDA didn’t immediately comment on what those criteria would include.

The FDA also on Friday approved a contraceptive vaginal ring that can be used for a full year.

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