Apple Watch Series 8 will give users a retrospective estimate of when they ovulated based on data from a new temperature sensor.

Using two sensors on the Apple Watch Series 8 the built-in menstrual cycle tracking app will check users’ temperature at the wrist every five seconds overnight. This should allow for ovulation tracking as body temperature changes over the course of the menstrual cycle, and rises in response to ovulation.

WatchOS 9 and iOS 16 will also include changes to the cycle tracking app that flag any abnormalities in a user’s menstrual cycle based on the data they input about their periods. Deviations from someone’s normal cycle — like more spotting than usual — can be a signal of health conditions like fibroids or PCOS, Sumbul Desai, vice president of health at Apple, said during the launch event.

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