The FDA has cleared the Apple Watch for use with Natural Cycles, a digital birth control app. This means Natural Cycles users who own an Apple Watch Series 8, 9, Ultra, or Ultra 2 can now import their temperature data from the watch instead of manually taking their basal body temperature each morning. This marks Natural Cycles’ second FDA-cleared wearable integration, with the first being the Oura Ring.
Apple Watch integration is a big deal, given that it held roughly 30 percent of the global smartwatch market in 2022, which is also the year Apple introduced temperature sensors on the Series 8. While it’s far from the first smartwatch to do so, Apple’s take was unique in that it incorporated two temperature sensors. One was located just underneath the display, while the other was located closer to the skin. The first is meant to take ambient temperature readings to help eliminate environmental bias. The sensors were also what enabled Apple to include advanced cycle tracking with retrospective ovulation estimates.
The Natural Cycles app requires people to input daily temperature data — from a basal body temperature thermometer, which is free with a subscription if you don’t have a compatible wearable — which is then fed into an algorithm that purports to inform users of their fertility status. It’s currently the only FDA-cleared digital birth control app in use and designated as a Class II medical device. Class II devices are those defined as having a moderate to high risk to the user and include things like blood pressure cuffs, contact lenses, and smartwatch EKG features used to detect atrial fibrillation. Popular period tracking app Clue had also received FDA clearance as a contraceptive in 2021 but has since paused that feature.
In a statement, Natural Cycles co-founder and CEO Elina Berglund Scherwitzl said the company received numerous requests from users to incorporate an Apple Watch integration once the Series 8 launched with the new temperature sensors. Older models of the Apple Watch do not include temperature sensors, nor do the SE models; only the Series 8 and 9 and the Ultra models are compatible with the feature.
The use of wearable temperature data for reproductive health tracking is a rising trend. Natural Cycles first pursued “wearable birth control” back in 2020 before receiving FDA clearance for this technology in 2021. It gained clearance for Oura Ring integration last year and, earlier this year, partnered with Samsung to adapt its algorithm for advanced Cycle Tracking for the company’s Galaxy Watch 5 and 6 series smartwatches. (The Galaxy Watches, however, are not compatible with Natural Cycles’ birth control features.)
The Apple Watch Series 8 introduced temperature sensors that enabled advanced cycle tracking. Older models of the Apple Watch do not include these sensors. Image: Amelia Holowaty Krales / The Verge
That said, Natural Cycles is not without controversy. The FDA initially granted the app clearance for its digital birth control feature in 2018, but the decision received some backlash after the app was linked to 37 unwanted pregnancies at a single hospital in Sweden. Furthermore, reproductive health apps have received increased scrutiny in the US following the Supreme Court’s reversal of Roe v. Wade in 2022.
Natural Cycles says for this integration, it had to submit clinical evaluations to the FDA via the agency’s 510(k) review process, as well as proof that the app complies with cybersecurity requirements for data privacy. In addition to the FDA, Natural Cycles says its Apple Watch integration has also received clearance from European regulators and has also been registered for use in Australia.
Even so, receiving regulatory clearance doesn’t mean these methods are foolproof. The upside to using temperature data from wearables is that it may eliminate some user error by adding another layer of automation, as well as providing more consistent data. However, it still requires consumers to adhere to using the app correctly, and user error can still result in unwanted pregnancies.