Ava is a Wearable Tracker That Can More Accurately Identify Fertility Windows

There’s an argument that says that regular sex is the most reliable way for a couple to get pregnant. That’s not right or possible for every couple, though, and many women have turned to fertility tracking to try to predict their ovulation cycles in the hopes of success. Until now, fertility tracking has been low-tech — for the most part, women have had a choice between basal body thermometers and ovulation sticks. But, with wearable fitness trackers on the rise, one company figured out that many of those sensors could be used to track, predict, and identify fertility windows. The result is a wrist-worn tracker called Ava.

Ava looks a bit like a fitness tracker, but without the display — perhaps comparable to the Misfit Shine, in that way. There are lots of similarities inside, too, with many sensors in Ava that are commonly found in other wearables. But, there are some key differences — I spoke with Ava co-founder Lea von Bidder, who made it clear that Ava is, at heart, a medical device. It fits much more snugly than fitness trackers, with a silicone band that feels a bit more elastic.

The tightness is to ensure accurate readings, and they do need to be accurate — Ava is promising much more reliable results than what basal body thermometers and ovulation sticks are capable of. Together with a companion app, Ava can identify fertility windows accurately from month to month, as soon as the first day. The wearable contains several sensors that collect data, which is analyzed by the app. The app then notifies women when their cycles have begun by, among other methods, changing the background color of the app. Conveniently, Ava is meant to be worn at night — that makes room for other wearables worn during the day, and also gives women a chance to recharge Ava when there are no other devices hogging up the USB ports (it does need to be charged daily).

Ava identifies fertility windows by using sensors that track resting heart rate, skin temperature, heart rate variability, sleep, breathing rate, movement, perfusion, bioimpedance, and heat loss. That data is either gleaned directly from familiar sensors — ambient and normal thermometers, an accelrometer, and an optical sensor for heart rate. The only uncommon sensor is a galvanic skin response sensor, which measures electric conductivity in the skin.

That data is filtered and analyzed by Ava’s algorithms, and one of the most important results is a prediction of the wearer’s estradiol levels. Ava can detect the subtle biological changes associated with an increase in estradiol production, instead of measuring hormone levels directly. Estradiol is one of the first hormones to spike when a woman’s ovulation cycle starts, and measuring it accurately is what allows Ava to pinpoint the first day of a woman’s fertility window, opening up the whole four to six day window.

The up-front cost of Ava ($200) is quite a bit higher than basal body thermometers or ovulation sticks, so I talked to von Bidder about how the wearable improves on those older methods. One of the key distinctions between Ava and basal body thermometers is that the latter are only predictive — by tracking temperatures daily for months, basal body thermometers can indicate around when a woman’s ovulation cycle starts every month. But, some women have irregular cycles, and beyond that, it’s rare for the fertility window to be open at the same time every month — because that’s only a four to six day window, a method that works give or take a day or two can be next to useless. von Bidder also pointed out that external factors like traveling or drinking can throw off thermometer readings, decreasing their predictive abilities. Add on the extra stress of manual recording, and it’s clear that it’s a dated method.

By using data to detect estradiol levels, Ava isn’t predictive — it’s actively identifying when the fertility window is open every month. On top of that, it’s non-invasive and requires minimal effort because the wearable and the app can work autonomously, alerting women when their fertility window is open automatically. While ovulation sticks can be better than basal body thermometers for actively identifying the start of a cycle, they aren’t as easy to use as Ava and can be become very expensive if the process of trying to get pregnant starts to drag on.

To prove their concept, the team behind Ava ran a study in March 2015 in Zurich. Actually, it might be more appropriate to reverse that — the team originally set out to make the temperature method more efficient, which led to the development of Ava. The Zurich study lasted for one year and involved 41 subjects whose ovulation cycles were monitored monthly. All of the women wore an Ava prototype — the researchers wanted to know how often Ava correctly identified each woman’s cycle every month. The result? Ava correctly identified a woman’s fertility window 89 percent of the time, with an average of 5.3 fertile days per cycle correctly identified. The team’s not done, either — a follow-up study involving 250 subjects is set to begin this year.

But, Ava is $200. It’s quite a bit more expensive than a basal body thermometer or ovulation sticks, although the latter might not be true if a couple needs to try for pregnancy for a year or more. Granted, no one method will ever be right for everyone, but Ava does have some strong arguments in its favor. For women with irregular cycles, basal body thermometers are nearly useless, and Ava could be a great way to get reliable information without the added stress of using ovulation sticks. It also has the advantage of being completely passive — it only needs to be worn and connected to a smartphone, with no manual recording necessary.


Ava has gotten some unexpected interest, too. von Bidder told me that Ava preorders have come from a wide variety of women, including those who aren’t looking to get pregnant and just want a reliable cycle tracker. Other women were keen on tracking data from Ava after they became pregnant, too — it doesn’t necessarily have to be consigned to the junk drawer once a woman has successfully conceived. Wherever the interest has come from, it seems to have been plentiful. While she couldn’t specify sales numbers, von Bidder confirmed to me that Ava had sold out its first two production runs ahead of their official launch.

Ava is available now for $200 directly from their website. The app is currently available for iOS only, but an Android version is in development. Right now, units are scheduled to ship out four to eight weeks after putting in an order, but Ava guarantees full refunds for anyone who gets pregnant before their tracker arrives.

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  1. I should probably get this and not just rely on my free ttckit OPKs. The $200 price tag is a bit steep but probably worth it if it does what they said it would.

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