Around one in seven couples can expect to struggle with infertility, with myriad causes from polycystic ovary syndrome (PCOS) to low sperm count. Many couples who are struggling to conceive will try and estimate the female partner’s ovulatory window in order to maximise their chances of getting pregnant. Traditionally this process has been carried out by a somewhat arduous combination of urinary luteinising hormone (LH) tracking, basal body temperature (BBT) measuring, calendars and calculations.

Now, tech companies across the globe are springing up to streamline the process, offering consumers software and devices designed to take the headache out of fertility tracking. With some firms claiming that their technology can double an individual’s chance of getting pregnant, more than a few eyebrows have been raised among fertility experts about the legitimacy of this technology.

Lister Fertility Clinic consultant gynaecologist and fertility specialist Dr Shabana Bora says: “If you’ve been trying for over 12 months, if you’re under 35, or six to 12 months if you’re over 35, and you’re not getting pregnant, the best thing to do is seek medical advice.”

Unscrupulous companies making money off the backs of people facing fertility problems is far from new. In July 2019, wellness company Get A Drip withdrew its £250 ‘fertility drip’ of vitamins and minerals from sale and issued an apology after experts accused it of exploiting vulnerable people with a false product. A May 2018, a review of 73 fertility apps in Current Medical Research and Opinion found that the best app was only able to achieve 21% accuracy in predicting a woman’s day of ovulation.

But Get A Drip’s product, sold alongside anti-aging, mood bosting and skin brightening IV infusions, was arguably sketchy from the outset, and the fertility app review focused purely on calendar apps rather than technologies which measure physiological parameters. Could companies that combine tracking apps with device technology fare better?

Basal body temperature

BBT is the body’s temperature at rest and is often used as an indicator of fertility, and can be measured orally, rectally, vaginally or through wrist skin. It’s a metric that’s tracked by many fertility devices.

Manual BBT tracking relies on a woman taking her temperature every morning before any activity. The lowest temperature occurs around the fertile window, corresponding to a peak in oestrogen, followed by a peak in temperature after ovulation, corresponding to a rise in progesterone. As the lowest point cannot be identified until the subsequent rise is noted, this is a retrospective measure of fertility tracking – it can alert somebody that ovulation has occurred, but not predict when it will next occur. Still, carrying out BBT over the course of a few months and tracking this on a calendar can help women narrow down when ovulation is most likely to occur.

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: predicting fertility with AI

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: juggling the data

OvuSense is a device worn in the vagina overnight, taking a temperature reading every five minutes. The company claims its device has a rate of 99% accuracy for detection of ovulation, with its predictive abilities clocking in at 89% with a positive predictive rate of 96%.

The data from these readings is downloaded into a smartphone app every morning, which used to indicate which point the user is at in their menstrual cycle. The OvuSense algorithm then processes this data through two methods, to predict the onset of ovulation and detect the date of ovulation. It then uses a further method to predict the fertile window at the start of each cycle, from the second cycle onwards.

OvuSense cites a 2000 study, which measured core body temperature over 11 cycles using a swallowed temperature probe, as proof of its concept. The study was able to show that core body temperature, as opposed to oral or external temperature readings often used in BBT tracking, could more accurately track progesterone levels and thus the stage of ovulation.

Much like Ava, OvuSense’s algorithms use this data to predict the when phase change of temperature after the lowest point will occur, and thus when ovulation is likely to happen.

“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 core temperature technology sounds impressive, she says, but measuring BBT after waking up in the morning is more than adequate for women using temperature to track fertility.

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.

A matter of convenience

The NHS says 84% of couples will get pregnant within a year through having regular sex without contraception, and NICE advises against ovulatory tracking during this initial period due to the stress it can cause. Failure to conceive after this period is often indicative of an underlying medical issue rather than poorly timed intercourse. Both Ava and OvuSense may have the data on-hand to attest to their accuracy, but what they lack is data to prove their usefulness.

Bora says: “In a world now where everything seems to be digitised and everyone is using their mobile phones, I think fertility tech can be appealing. But if you’re one of these people who’s been trying for a long time I’m not sure buying a tech device is going to increase your chances of pregnancy.”

Manually charting and tracking fertility through BBT and LH tests can be arduous, and many women may favour medical devices like Ava and OvuSense due to the convenience the technology can give them. But if a condition like low sperm count or endometriosis is responsible for failure to conceive, even the most high-tech method of ovulatory tracking can only go so far.

“Technology can be very helpful to people who are struggling with infertility, but it’s also important that the results of that research are explained to patients in simple terms so they can make an informed decision about what is right for them,” says Trigo. “Speaking with a healthcare professional is the way forward to understand research and be informed so people can make an informed decision about their fertility.”