Can wearables turn temperature into a pregnancy test?

Can wearables turn temperature into a pregnancy test?

Yesour smartwatch may alert you to an irregular heartbeat. Your phone can assess your risk of falling. And now, research suggests that temperature trends picked up by wearable devices can tell you if you’re pregnant before you even think about taking a test.

By examining temperature data from 30 women who became pregnant while wearing an Oura ring, researchers from the University of California, San Diego, found that nighttime maximum temperatures were significantly higher two to nine days after intercourse that ultimately led to conception. In retrospect, they showed how this change in temperature could have been used as a passive pregnancy notification – a notification that, for these users, would have appeared around nine days before they received a positive test.

If the idea comes to fruition, it could prove a compelling use of wearable data, which has so far struggled to significantly change the course of clinical care.


“If women know they’re pregnant earlier, they can make choices about their lives that they might not otherwise know,” said co-author Benjamin Smarr, a professor in the Departments of Bioengineering and Data Science from UCSD. This could mean taking steps like avoiding smoking and drinking during the sensitive early stages of pregnancy development. Detecting pregnancies earlier could also become critical if the Supreme Court repeals Roe v. Wade, removing federal abortion protections. “You could also say I don’t want a pregnancy, and if you know that sooner, you know there are even more legal options available to you,” Smarr said.

The fact that body temperature rises after conception is well understood, as are the temperature changes that occur throughout the menstrual cycle, which some people monitor with a standard thermometer to avoid or plan pregnancy. “Amazingly, if you pay attention to a woman and she gets pregnant, her physiology changes and you can see that,” Smarr said. “It’s not rocket science.”


But it can be difficult to get a reliable trend with just one daily measurement. A thermometer reading can be skewed by sleep quality, time of day, or even getting up to pee in the middle of the night. Researchers like Smarr, who received pay from Oura as a scientific adviser, say collecting temperature throughout the day can detect fine signals that can reflect a wide range of hormonal cycles and changes. , including those associated with pregnancy.

While the study showed temperature could cut pregnancy detection times by two-thirds in this small group, Smarr suggests the improvement is likely a floor, not a ceiling. The study was based on historical data from the first 30 Oura users who completed a questionnaire, had enough consistent data, and became pregnant – a self-selected group who were already fairly committed to fertility data. At the population level, it’s unclear when women typically find out they’re pregnant, but what little research there is suggests that passive alerting could cut the time before they find out by weeks.

“There’s all this fruit at your fingertips,” Smarr said. “Let’s go get him.”

There is more refinement to be done, of course. Temperature-based alerts for pregnancy should be accurate in a much larger population than the predominantly white, economically safe and educated user base being studied, Smarr said.

“Getting this to a place where it’s equitable and reliably serves a large population is not easy,” Smarr said. “It requires all sorts of regulations and policies and a private partner ecosystem, of which wearable companies will be a part.”

In a follow-up study of a larger and more diverse user group, Smarr expects to find more variability in temperature patterns that could influence how an algorithm would identify a likely pregnancy. “We want to make sure we do our due diligence on this before we just say, ‘Hey, here’s a one-size-fits-all. “” The same caveats apply to fertility tracking; Another study based on Oura led by Smarr co-author Azure Grant from 2020 showed that the device’s temperature and heart rate variability could be used to generate a signal predictive of ovulation.

Another question: is continuous temperature data really much better than that collected with a simple thermometer?

“That’s a tough question, because there really isn’t any data to make that comparison,” said Neta Gotlieb, a former colleague of Smarr at UC Berkeley who now works as a senior clinical researcher at Oura.

The relative value of continuous data will depend on the cost of the devices, their precision, and the variability of the measurements. Wearable devices typically capture wider ranges of skin temperature, not core body temperature, with fluctuations that provide useful variance or frustrating noise depending on the application. The gain will also depend on how their signals are integrated – or not – into clinical care. Although consumer wearable devices collect a lot of data that could theoretically be used in healthcare, it is still rare that patients or their healthcare providers can act on an alarm signal triggered by a device. And since most fertilized eggs fail to implant, there is also concern about unnecessarily alerting users. “It adds that extra level of complexity, the ethical or emotional burden of knowing too soon,” Gotlieb said.

But a passive pregnancy alert — which could be just as effective for women trying to conceive as it is for those for whom it’s the furthest thing on their mind — is a goal Smarr still thinks is worth the effort. to reach. Although Oura does not provide any alerts related to pregnancy or fertility, users have reported realizing they might be pregnant while tracking temperature trends themselves.

“There’s no point in exaggerating that we would replace the pregnancy test, that’s not the intention,” Smarr said. “One day, would it ever be? It probably would. Are we already there? Nope.”

This future may become more realistic as more wearable devices begin to incorporate temperature measurements. Oura was the first wearable to incorporate measurement, leading to the research partnership with UCSD (Grant also received compensation from Oura as an intern). Watches from Fitbit, Garmin and Amazon have since incorporated temperature, as have some wearables for fertility tracking, such as the Ava watch band.

And wearable companies seem poised to build a female customer base — and a pool of female research participants. Only 40% of Oura users are women, Gotlieb said, and “women’s health is one of Oura’s main areas of investment.” This week, the company is launching a study with Creation, a leading US fertility care provider, to study the physiological correlates of the menstrual cycle using the ring. “Because women have historically been understudied in clinical trials and drug trials, we’re still at the stage where we’re learning basic physiology before we can study applications,” Gotlieb said.

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