Cashing in on fertility: should femtech receive more scrutiny?

inFertile Life founder Dr Andreia Trigo says: “BBT charting requires a high degree of patient compliance, ability to interpret the chart and account for several factors that can affect the temperature readings: consumption of alcohol, late/disturbed night, oversleeping, holidays, travel, time zones, shift work, stress, illness, medications.”

Two devices that use body temperature to track fertility are Ava and OvuSense. Both wearables, they can help cut out the hassle associated with manually charting BBT – for a pretty penny or two.

Ava costs £249 outright, while OvuSense retails between $129 to $299 depending on the subscription purchased to its app.

Ava is a wearable sensor worn like a bracelet overnight. As well as tracking temperature through the wrist it measures four other physiological signs of fertility – heart rate, heart rate variability, skin perfusion and respiratory rate. Using an artificial intelligence (AI), the bracelet corroborates these measurements to give the wearer a prediction of their fertile window. A recently published study in the Journal of Medical Internet Research indicates that the algorithm was able to detect the fertile window with 90% accuracy.

Ava’s website states that it can double a user’s chance of getting pregnant, a statistic sourced from a secondary study which demonstrated that intercourse timed during a woman’s fertile window could increase her probability of conception.

Ava CEO Lea von Bidder says: “Women have known for centuries that temperature increases after the fertile window. If we now use everything that technology has to offer, we’ve been able to find factors that correlate with the menstrual cycle earlier. We can use our knowledge about those changes to detect earlier and with higher accuracy.”

However, fertility experts remain divided on whether the algorithms inside Ava are worth the cost. While Trigo feels that tracking several parameters will be more reliable than just one, Bora remains unconvinced.

“I don't understand why Ava is any different from using just one single measurement, using an LH ovulation kit or doing something much simpler like taking a rectal temperature measurement,” Bora says. “You’re not going to predict your time of ovulation any more accurately.”

Ava also states it can only be used by women with menstrual cycles ranging between 24 to 35 days, and is unsuitable for those with PCOS, hormone imbalance or highly irregular cycles – the women who are most likely to be the ones struggling with their fertility. However, von Bidder maintains this is a regulatory issue, rather than an operational one.

“In order to claim a medical device for any subgroup we would have to include them in our study, which we haven’t done yet,” von Bidder says. “However, we are aiming to carry out a further study because we believe we can make this work for women with PCOS.”

OvuSense is a sensor worn in the vagina overnight, taking a temperature reading every five minutes. The data is then downloaded into a smartphone app every morning, using the temperature readings to indicate which point the user is at in their menstrual cycle.

OvuSense claims a rate of 99% accuracy for detection of ovulation, with its predictive abilities clocking in at 89% with a positive predictive rate of 96%.

This data has been shown on conference posters at annual meetings of the European Society of Human Reproduction and Embryology (ESHRE) and the American Society for Reproductive Medicine (ASRM) rather than in peer-reviewed journal studies.

OvuSense CEO Robert Milnes says: “We have chosen to publish posters at conferences very deliberately because that gets the data out into the public domain much more quickly. Essentially that’s on a six-month timeline rather than the space of 18 months or so it takes to get published in a journal.”

Poster publications are reviewed by the committee of peers for both societies before being permitted and are later published in official society journals.

“Other devices predict based on past-month data for what’s going to happen in the current month,” says Milnes. “We don’t do that, we predict using current cycle data.”

“If you have a regular 30-day cycle, it’s not uncommon to ovulate on day 14 in one month and day 17 in the next. We’re able to detect that ovulation and predict it in the second month when it’s day 17 just as easily as we’re able to in that first month when it’s day 14 because of the fact that we’re tracking more accurately what’s happening to the temperature over that period of time.”

However, Trigo says even with OvuSense women with irregular cycles will still struggle to receive accurate results, despite the company’s claims.

Trigo says: “For those with irregular cycles or hormone imbalance, OvuSense will still detect ovulation when this occurs, but the fertile window prediction for the next cycle could be out by a few days.”

She is also sceptical as to whether taking a temperature reading every five minutes overnight is entirely necessary, and ultimately suggests women look into LH testing. OvuSense’s technology sounds impressive but measuring BBT after waking up in the morning is more than adequate for women using temperature to track fertility, she says.

While Milnes says that UK National Institute for Health and Care Excellence (NICE) guidelines discourage general practitioners from recommending LH testing to their patients, a NICE spokesperson said this was not the case.