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A subtle yet significant biological change occurs in the body: post-ovulation, body temperature rises by approximately half a degree, dropping again as menstruation approaches. While this may go unnoticed by many, it’s a crucial detail for those tracking ovulation, aiding in family planning or pregnancy prevention. The Oura Ring, a wearable primarily recognized for sleep monitoring, leverages this data, among other metrics, to forecast menstrual cycles.
When I was trying to conceive my first child, I recall meticulously monitoring my temperature. At the time, this required purchasing a specialized thermometer with an extra decimal precision (e.g., 98.62 instead of 98.6). It was essential to measure temperature immediately upon waking, at the same time daily, to ensure consistency. Recording this data in a journal or on a fertility-tracking platform allowed me to identify ovulation within a day’s accuracy.
The optimal window for conception is the few days leading up to ovulation, making precise tracking invaluable. Conversely, for those avoiding pregnancy, temperature-based fertility awareness can be a useful tool—though it’s less reliable than IUDs, birth control pills, or condoms. (Planned Parenthood offers further details on this approach here.)
Initially, I questioned whether the Oura ring's reliance on skin temperature for 'readiness' scores might be disrupted by ovulation. This was indeed the case early on, but the company soon recognized the potential of temperature tracking for users who ovulate. Beyond aiding pregnancy planning, monitoring temperature can also provide insights into your menstrual cycle.
For those with a 28-day menstrual cycle, ovulation typically occurs around the midpoint, approximately two weeks after the start of your period. If your cycle is longer, the first half tends to extend—for example, three weeks from menstruation to ovulation, followed by two weeks from ovulation to the next period.
How the Oura app functions
While devices like the Ava wristband focus on temperature tracking for fertility, Oura isn’t exclusively designed for conception. However, the company revealed that the latest version of their ring will incorporate a menstrual cycle prediction feature in its app. The previous model allows temperature monitoring and period logging, but the new version introduces predictive algorithms.
(A key update for current or prospective Oura ring users: the company has shifted its business model. Previously, purchasing the ring granted free access to its features—unlike Whoop, which offers the device for free but charges a subscription fee. Now, Oura requires payment for both the ring and a subscription. Current users can upgrade for a lifetime subscription, while new customers receive a 6-month membership. Older models will continue functioning as before. Gizmodo provides additional details on the new ring and its features here.)
Based on the company’s research, such as a study published last year, the ring can detect shifts in temperature and heart rate variability—metrics it already monitors for sleep and health tracking—to anticipate the hormonal surge associated with ovulation.
The period prediction feature will launch first on iOS, followed by Android, according to the company. To activate it, users can enable it in settings or via a prompt on the home screen, then provide details about cycle length and regularity. Once set up, the ring monitors temperature, and users log the start of each period. Here’s the company’s guide to the new feature.
Accurate predictions typically require about two months of data. After this period, the app will forecast your menstrual cycle, offering a 30-day estimate, a six-day reminder, and a final alert the day before your period.
The company notes that while the feature is designed to work for cycles of varying lengths, its accuracy may be compromised for individuals using hormonal birth control, IUDs, or hormone replacement therapy, as these can suppress the temperature fluctuations the ring relies on.
