Natural Cycles is an app marketed as “a natural method of contraception that is powered by a smart algorithm” with the goal of “empowering women.” Last week, it became the first app approved by the FDA to prevent pregnancy.

The Swedish-based company had been cleared in Europe in 2017 and is an emerging name within the “Femtech” industry a catch-all for “female health technology” that has reaped an estimated $1 billion of investment worldwide in the past three years.

Clinical studies to screen Natural Cycles’ effectiveness for use as a contraception included more than 15,500 women who used the app for an average of eight months. Of those who used the app perfectly as directed, 1.8 percent became pregnant (what is known as the “failure rate”), according to the FDA. The app had a “typical use” failure rate of 6.5 percent, and accounted for women who sometimes didn’t use the app as directed and had unprotected sex on fertile days.

For comparison, the CDC’s failure rate of birth control pills is roughly 9 percent. Hormonal IUDs have failure rates of less than 1 percent, and condoms roughly 18 percent. And in fact, the only fool-proof way to avoid pregnancy is to not have sex.

But not all are convinced that the app represents the future of contraception, or should even be used now. Gynecologists and women who have used the app caution that it requires a level of diligence: The app is only as good as the information women enter. And they point to incidents of unexpected pregnancies by those who have relied on it.

How it works

Natural Cycles calculates which days of the month a woman is likely to be fertile based on information she enters about her menstrual cycle and basal body temperature. The method, often referred to as fertility awareness-based method, identifies the days per menstrual cycle in which a woman is fertile.

Women using the app must take their temperatures immediately after waking up each morning using a basal body thermometer. Basal body thermometers are more sensitive than others. The thermometer comes with the app, which costs $79.99 annually.

Juan Acuna, an ObGyn specialist at Florida International University and an adviser to Natural Cycles, said there has been a long-standing view that natural contraception like the rhythm method, for example was not fail safe to prevent pregnancy in women who are fertile and having sex without other forms of contraception. Natural contraception requires women be educated about their cycles and willing to map out when they are fertile.

A program like Natural Cycles runs those calculations, he said.

Still like most other forms of birth control, Acuna said women shouldn’t solely rely on the app during their first few cycles of using it.

“It helps fill a vacuum in the world of natural contraception,” Acuna said.

A ‘high-maintenance’ method

Before its approval in the United States, the app came under fire when a Swedish hospital reported that more than three dozen women who had used Natural Cycles as their sole birth control sought abortions there between September and December 2017. The company said that the number of pregnancies, in proportion to the registered number of Swedish users, was “in line with our expectations,” The Guardian reported.

Laura MacIsaac, associate professor of obstetrics, gynecology and reproductive science at the Icahn School of Medicine at Mount Sinai, said Natural Cycles was “a little more exciting” in that it tracks both menstrual calendars and basal body temperature.

But she cautioned against forms of contraception that require such intense maintenance and attention, especially for women seeking long-term pregnancy protection. Even women who obsessively comply with the program will be fertile for a stretch of every month, MacIsaac said. She added that contraception methods that are highly labor intensive are also the hardest to stick with.

“High-maintenance methods are the ones that have the highest failure rates, not because they don’t work biologically but because they don’t work in normal peoples’ lives,” MacIsaac said. That can include women who travel or have otherwise unpredictable schedules, or women who cannot ritualistically take their temperatures before doing anything else in the morning.

“Whoever could do that, I don’t know those women,” MacIsaac said.

Last month, a woman detailed her own experience getting pregnant while using Natural Cycles and subsequently having an abortion. Writing in The Guardian, Olivia Sudjic described the shame she believes leads other women not to report their unplanned pregnancies.

Sudjic said she was drawn in by the promise of a hormone-free, noninvasive contraceptive, only to wind up feeling “colossally naive.” Another woman quoted in the piece who got pregnant and had an abortion said she felt ashamed.

“I felt like I’d acted alone in the decision to use the app and had been overly trusting. But I was also angry that I’d been treated like a consumer, not a patient,” the woman told Sudjic.

For her part, MacIsaac added one more reason she wouldn’t recommend Natural Cycles to her patients.

“I think the way technology can make women more healthy and happy,” she said, “better sleep and healthier sex lives: Get your phone out of your bedroom.”

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