At the NWHN, we have been long-time skeptics of Natural Cycles, a smartphone app that markets itself as a reliable birth control method. Natural Cycles uses a high-tech version of the “rhythm method,” where users track their menstrual cycles in order to prevent an unplanned pregnancy. The app relies on data uploaded by the user — such as daily basal body temperature (BBT) readings — to make predictions regarding fertility. (BBT is body temperature when one is completely at rest.)

In November 2020, Natural Cycles announced a partnership with Oura Health, a company that manufactures the Oura Ring, a “wearable” (like a FitBit or Apple Watch) worn on the finger that tracks sleep patterns, heart rate, and temperature. The new Oura Ring feature would collect users’ BBTs overnight and upload that data to the app. (Consumers can currently access this feature through a beta program.) 

The integration of Oura into the Natural Cycles system raises even more concerns for us. While Natural Cycles itself is FDA-cleared, potential users should know that the Oura ring has not been cleared by the FDA as a medical device. There is also very little independent data about the Oura ring’s effectiveness, as Oura Health controlled the studies that have been completed so far.

Furthermore, thermometers that are used to measure BBT require a greater degree of sensitivity than the standard thermometers used to measure fever temperatures. If the Oura ring isn’t accurate enough to track these subtle temperature changes while filtering out the temperature changes that are unrelated to fertility, the likelihood of false Natural Cycles predictions increases. Ultimately, this could increase the chance of an unplanned pregnancy. 

Natural Cycles is currently only permitting fertility tracking users, not contraceptive users, to use the beta Oura Ring feature. However, Natural Cycles is promising that “Wearable Birth Control” is “coming soon,” implying that the Oura Ring will soon contend with birth control pills, Long-Acting Reversible Contraceptives (LARCs), and other methods .This is extremely misleading, and could lead consumers to believe that wearing the Oura Ring on its own will prevent pregnancy, when in reality, it’s just a very expensive thermometer for fertility tracking. If it’s unreliable as a BBT thermometer, it could compound errors in the predictions that Natural Cycles’ users rely on when deciding whether its safe to have sex.

Finally, pairing the Oura ring with the Natural Cycles app ensures that two companies have access to some of the most private user data available, with few real constraints on how they use that data. If the ring is as accurate as its makers hope, it will mean both companies will know when a user is pregnant, or has had a miscarriage or an abortion. This could have frightening future implications, as conservative lawmakers have sought to roll back health care protections for those who have had miscarriage(s) or abortion(s).

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