Not all fertility apps are created equal

A new study examines what you should know and what you should look out for in fertility-tracking apps.

5 minute read

Unlike most people in the world these days, I do not have an intimate relationship with my cell phone. Sure, it can pull off a video call and take a good picture, light up a dark hallway and rouse me in the morning, but the phone and I are not close. I don't share much with it. It doesn't know my weight or exercise routine or bank login details, for instance, and it doesn't keep track of my appointments or my coffee orders. Truth be told, I haven't even told it my location. 

So I suspect a fertility-tracking app is not something that would ever have appealed to me. But I respect that it might be very attractive to others. 

Women spend a lot of mental energy staying on top of their monthly cycles, for all sorts of reasons, so enlisting the help of an app makes good sense. It could help with predicting when a period is due, with trying to get pregnant, or, conversely, with trying not to. 

In the old days, women were taught to count 14 days back from the expected start of their next period and call that ovulation day. That's the calendar method. As you can imagine, it has obvious drawbacks for anyone with an irregular cycle, not to mention anyone who has recently given birth, is breastfeeding, is approaching menopause or is under a lot of stress. It also ignores the fact that women just naturally vary in when they ovulate.

The "fertile window" — the time during which a woman can get pregnant — is roughly ovulation day and the five days that precede it. To figure out when that falls, more sophisticated techniques add information about daily basal body temperature, a measure of your lowest temperature during rest, and changes in the consistency of cervical fluid. A rise in temperature of 0.2 to 0.4°C could signal ovulation, as could an "egg white" consistency in fluid. Throw in a test strip that measures levels of luteinizing hormone in your urine and you can make a fairly accurate prediction.

But it's a lot of work — not just to gather those data but to analyze them. Which is why there's an app for that. Many apps, in fact.

Joyce Harper, a professor of reproductive science at University College London, and her colleagues Zeynep Gurtin and Roshonara Ali, decided to look into these apps. After a careful trawl, they identified 90 separate apps that tried to predict ovulation, predict the fertile window, or assist in conception (along with a few other criteria). 

The researchers examined how each of the apps worked and what features they offered. Almost all of them asked women to input information on their calendar dates. Many of them also asked for data on temperature, cervical fluid or luteinizing hormone, or some combination of the three. 

Below, I share seven of the interesting things they discovered about fertility-tracking apps. 

1. Just because you input it doesn't mean they use it...

The most astonishing finding to me was that several apps ask women to go to the trouble of tracking things like daily basal body temperature or cervical fluid consistency — and then they just ignore it all! These apps are no more than glorified calendars, say the researchers, but they pretend to be more. "It is, therefore, extremely important that users are made aware that the time, effort and cost they spend measuring such fertility indicator measures may be wasted," the researchers write, "and that the apps may not actually be refining their fertility predictions based upon these indicators."

That said, some actually do use these data, the authors say, although their methods vary and are not always easy to make out.

2. The free apps may be better than the paid ones...

Twenty-two apps were for sale, priced, in the UK, between £0.99 and £9.99. Sixty-eight apps were free to download, but some of them require additional purchases, and those costs ranged from £1.99 to £363.48 a year. Thirty-one apps were truly free, though, costing nothing at all. 

Much to the authors' surprise, the apps that were free to download tended to be better than the ones you pay for — they were more likely to have additional features like mood, weight, sleep and intercourse trackers, the researchers found, and they had "more and better quality educational insights." Downside? Ads.

3. Fertility-tracking apps are somehow not regulated...

Europe's Medical Device Directive says that a software product can be a medical device. The UK's Medicine and Healthcare Products Regulatory Agency (MHRA) says that a medical device can be something that uses data to perform a calculation. Alas, these apps don't appear to be regulated. You're on your own. This is a "major concern," the authors write.

Despite that, only nine apps had warnings saying they weren't medical devices and shouldn't be trusted for medical purposes, the researchers found. Five warned they shouldn't be used for contraception. Eighteen admitted they might not be accurate.

4. Some apps are more social than others...

Thirty-eight apps allowed users to share their tracked info with others — doctors, partners, whoever. Others had communications features, private messaging, forums or even direct access to health coaches. Thirty-two linked to other apps like AppleHealth, FitBits or Google Calendar. 

5. One app had a parental control feature...

It was called "Magic Girl Teen." 

6. One fertility-tracking app was listed under "entertainment"...

Most were found in the "health and fitness" category.

7. Two fertility-tracking apps specifically targeted men... 

Eighty-one apps targeted only women, and seven targeted both women and men. Two apps — the "Female Calculator for Men" and the "Period Tracker for Men" — were just for guys. Think about that.

The researchers say that only apps that measure at least one fertility awareness-based method (like temperature or cervical fluid) should be allowed to be marketed as a fertility-tracking app. "It is alarming that calendar apps were found to be the most commonly available [fertility-tracking apps], accounting for 54.4 percent of apps in the present study," they write. "These apps are giving women inaccurate information about their fertile window."  


Roshonara Ali et al. "Do fertility tracking applications offer women useful information about their fertile window?" Reproductive BioMedicine Online. 2020. 

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