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Why This Fertility App's First Scientific Study Is So Exciting

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Photo: Victoria Song (Gizmodo)

Unless you’re a tech-savvy woman looking to get pregnant, you’ve probably never heard of Ava. Slim and discreet, it’s a $300 wearable tracker that in tandem with its companion app monitors your heart rate, body temperature, and breathing while you sleep to predict when you’re ovulating. None of that is particularly exciting on its own—after all, there are plenty of wearables or period and fertility tracking apps out there. (Ava launched its first device in 2016.) What is exciting is that today, Ava released a clinical study detailing how wearables can offer women a more accurate, noninvasive way to predict fertile days during their menstrual cycle.

When it comes to femtech, the blanket-term used to describe any women-specific tech regardless of whether its an app or a breast pump, that’s a big deal because the options out there are limited at best. For the thousands of free period and fertility tracking apps out there, barely any have conducted or participated in clinical research. Contraceptive app Natural Cycles has done some work, but it’s plagued with accusations of inaccuracy and flippancy regarding privacy. Meanwhile, a 2016 study from Columbia University Medical Center found that of 1,116 free period apps in Apple’s App Store, only 20 were accurate. More depressingly, only five percent cited professional involvement or cited medical literature.


That’s disturbing given the current climate surrounding women’s reproductive health. Regardless of where you stand in the abortion debate, it’s clear that we’re not all equally informed at what stage a missed period might be indicative of pregnancy, regular anovulation, or a symptom of a non-pregnancy related condition. Given the significant advances in technology over the past 20 years, you’d think there’d be better options than repackaged versions of the old paper calendars and diaries women have been using for centuries.

Ava’s study, titled “Wearable Sensors Reveal Menses-Driven Changes in Physiology and Enable Prediction of the Fertile Window,” is encouraging. The study had 237 women wear an Ava tracker for a year or until they became pregnant to measure five different parameters: resting pulse rate, respiratory rate, heart rate variability, skin perfusion, and basal body temperature. In total, the study analyzed over 1,000 cycles to try and find new patterns that could be used to more accurately predict a six-day fertile window for women trying to conceive. In it, Ava concluded that wearables were not only able to accurately and simultaneously track multiple physiological parameters during a menstrual cycle, Ava also developed an algorithm that could predict to 90 percent accuracy a woman’s six-day fertile period. While it only observed women with normal cycles—up to 30 percent of women experience irregular periods during childbearing years—that 90 percent is impressive. A separate clinical study from 2018 for smartphone apps surveyed 73 fertility apps, and fewer than a third could predict a six-day window or smaller, and with accuracy falling between 11 and 81 percent.


“This study is only the first in several planned studies that should validate the potential of combining machine learning, continuous monitoring, continuous monitoring, and technological innovation to improve women’s health care,” Ava Chief Medical Officer Dr. Maureen Cronin said in a press release for the study.

According to the study’s results, wearable tech also delivered similar readings to more traditional fertility tracking methods—but in a noninvasive way that offered more flexibility and convenience. For instance, current methods can involve women having to take their temperature at the same time every day, urinating into a cup to measure their luteinizing hormone levels, and studying their cervical mucus discharge.

A wearable that can accurately predict a woman’s most fertile days would have huge implications. On top of being more comfortable, it’d be a big step in giving women more in-depth knowledge about their bodies—and thus more autonomy. A more informed understanding of one’s cycle could also de-mystify what days would be most effective for couples to conceive. Who knows? In the long-run, there’s a chance that could reduce the number of families having to opt for expensive treatments that don’t come with a guarantee. It’s encouraging to see that Ava’s resulting algorithm from the study was able to predict a six-day fertile window with 90 percent accuracy. That’s still a ways from 100 percent, but it’s a start.

Ava’s study has some limitations. “The journal the study is in is an open access ejournal,” Dr. Margaret Long, an obstetrician and gynecologist at Mayo Clinic, told me in an email. “These are generally less rigorous journals.”

When I asked Ava about this, Dr. Cronin said it was a deliberate choice as open access journals don’t place research behind paywalls. “Beyond our wearable device, we want to help push forward scientific knowledge about women’s reproductive wouldn’t sit right with us to have found these phase-based changes and not make them accessible to absolutely everyone.” (Cronin told me Ava’s research was innovative enough to entice her out of retirement after a 20-year career developing various contraceptive methods for Vifor Pharma and Bayer Pharmaceuticals.)


Secondly, it’s important to note that Ava has an interest in the success of its product. I spoke with founder and CEO Lea Von Bidder and Dr. Cronin, and while I believe both are passionate about moving women’s health forward, it’d be naive not to acknowledge the possibility of industry bias. Still, its findings could be instrumental in pushing forward collaboration between tech and medical sectors—if it can gain traction.

That collaboration is desperately needed, especially when you consider Daysy—a $330 thermometer that claimed it could identify whether a woman was fertile up to 99.4 percent accuracy. That’s an absurdly high number, especially when you consider that multiple studies have found basal body temperature alone to be unreliable. A reproductive health researcher at the Guttmacher Institute raised concerns about the claimed number, and the study was eventually retracted over fundamental flaws in its methodology. It’s cynical, but published studies can be a compelling form of marketing. In Daysy’s case, it’s lucky a researcher happened to stumble across the company’s shoddy science and decided to speak up about it. Greater collaboration with researchers could’ve prevented that, or at the very least, saved consumers from a product that made promises it couldn’t realistically deliver. After all, when it comes to conception or contraceptive femtech, trust is paramount—even if it means less sexy marketing.


“I agree that the technology in [Ava’s] study is intriguing and may assist in identifying fertile days within a cycle,” said Long from the Mayo Clinic. “This is an exploratory study that can help guide future research, but the interpretation of data and also possibly the technology need refinement before it would be ready for general use.”

Dr. Long went on to explain that one issue is that for fertility tech to be trusted, it has to be certainespecially when it comes to the possibility that wearables could be used in the future as a contraceptive. “An error in regards to avoiding pregnancy can result in an unplanned pregnancy,” Long said. “An error in regards to identifying the fertile window means attempting pregnancy the next month.”


This highlights a huge obstacle facing wearable makers trying to make the leap from fitness trackers to bonafide medical devices. It was a big deal when Apple got FDA clearance for its Apple Watch’s ECG feature. Likewise, Omron’s HeartGuide blood pressure smartwatch required two years of clinical testing before it could hit the market. If we want to see FDA approval for a device like Ava before our ovaries shrivel up and die, that means more clinical research, more funding, more prototypes, and perhaps most frustratingly, a sense of urgency.

Ava’s study is preliminary and intriguing, but the fact is, it can’t do much on its own. Ava told me it has more studies on the way, including one comparing how Ava’s tracker fares against period apps solely based on population statistic data, as well as how Ava might help women with irregular periods. Still, even multiple studies from one company aren’t nearly enough. This is a good start, but unless it sparks a greater conversation within the industry, a good start is all it will ever be. Women deserve better alternatives than what’s out there, and it’s not unreasonable to ask that tech companies with big pockets and an interest in the health market play a bigger role in that. Women deserve to have their health given more time, effort, and funding than what they’ve been given.