The human body has a small peculiarity that many of us can live our entire lives without noticing: Body temperature rises by about half a degree after you ovulate, and decreases again when your period begins. If you do not ovulate personally, you probably do not care. If you do, this fact can be very helpful in planning (or trying to avoid) pregnancy. And Oura, the annular portable, especially known as a sleep trackercan use it now (along with other data) to predict your period.
I remember watching my temperature when I was trying to get pregnant with my first baby. At the time, you had to buy a special thermometer at the drugstore that had an extra decimal place (so you are not only 98.6, but, say, 98.62). You need to make sure you measure your temperature first thing in the morning, when it is most consistent, and always at the same time. And if you were watching in a notebook or on a special fertility website, you would be able to determine when you ovulated within about a day.
You will most likely get pregnant in the last few days before ovulation, so knowing when that time comes each month is extremely helpful. And if you prefer not to get pregnant, temperature-based fertility awareness can help with that too – although, as you might guess, it is not as effective as IUDs, oral contraceptives or barrier methods such as condoms. (Planned Parenthood has more information on this method here.)
When I first heard about how the Oura ring uses skin temperature as one of the factors that determines your “readiness”, I was wondering if it means that ovulation can lower the scores. And that was true, at least at first – but then the company realized that temperature tracking could be valuable for carriers who ovulate. Not only can you keep track of your temperature if you are interested in getting pregnant, it is also a great way to know where you are in your cycle.
If you get your period every four weeks, ovulation usually occurs right in the middle, about two weeks after your period begins. If your cycle is longer, the first half will usually be longer — say three weeks from menstruation to ovulation, but then two weeks from ovulation to your next menstruation.
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What the Oura application does
There are other devices out there that detect temperature changes for fertility, such as the Ava bracelet. Oura is not specifically aimed at baby-making, but the company has announced it the new version of their ring will include a period prediction function in its application. The old one will still allow you to see your temperature and mark days as period days, but the new one adds prediction algorithms.
Importantly, if you have an Oura ring or are considering buying one, the company has just changed their business model. Instead of buying the ring and getting its functionality for free — unlike Whoop , which gives you the technology for free and then asks for a subscription — Oura now asks for the ring and plan to charge for a subscription. They now offer offers to upgrade and get a lifetime subscription if you already have a ring, and they include a 6-month membership for new customers. If you plan to stay with your older model, it will still continue to work as before. Gizmodo has more about the new ring and its features here.)
According to company studies, including this one published last yearthe ring is able to pick up changes in temperature and heart rate variability (two things it measures anyway in the course of sleep and health detection) that predict the hormone surge that occurs around ovulation.
Deadline prediction will be available immediately in iOS, the company says, and shortly thereafter in Android. To set it up, you’ll turn it on in settings (or from a map that appears on your home screen), and then you’ll answer a few questions about how long and how frequent your cycles tend to be. After that, the ring will track your temperature and you will let it know every time your period starts. Here is the company’s guide to the new feature.
It takes about two months to start getting accurate forecasts, and then the application will be able to tell you every month when it expects your period. You will receive an estimate 30 days in advance, a reminder six days in advance, and a reminder the previous day.
The company has an indemnity that, although the feature should work on cycles of all lengths, they do not expect it to be accurate if you use hormonal birth control, have an IUD or use hormone replacement therapy, as you do not necessarily have the changes in temperature it expects.