Use Cycle Tracking on Apple Watch Ultra
Use the Cycle Tracking app 
to log details about your menstrual cycle. You can add flow information and record symptoms such as headaches or cramps. Using information you’ve logged, the Cycle Tracking app can alert you when it predicts that your next period or fertile window is about to start. If you wear your Apple Watch Ultra to sleep each night, the app can use wrist temperature to improve period predictions and provide retrospective ovulation estimates. For more information, see the iPhone User Guide and the Apple Support article Track your period with Cycle Tracking.
Siri: On Apple Watch Ultra 2 using watchOS 10.2 or later, say something like: “Log that my period started today.” (Not available in all languages or regions.)
Note: The Health app is designed to protect your information and enable you to choose what to share. Learn more about how the Health app is built to keep your data secure and protect your privacy.
Set up Cycle Tracking
Open the Health app on your iPhone.
Tap Browse at the lower right to display the Health Categories screen.
Tap Cycle Tracking.
Tap Get Started, then follow the onscreen instructions to set notifications and other options.
To add or remove options after setting up Cycle Tracking, open the Health app on your iPhone, tap Browse, tap Cycle Tracking, then tap Options next to Cycle Log.
Log your cycle on Apple Watch Ultra
Open the Cycle Tracking app
on your Apple Watch Ultra.Do any of the following:
Log a period on a specific day: With the day showing in the timeline, tap Log. Tap Period, tap a flow level, then tap Done.
Log symptoms, spotting, or other information: With the day showing in the timeline, tap Log. Tap a category, choose an option, then tap Done.
The observations you provide appear in the Cycle log on iPhone. If you’ve turned on Period Notifications and Fertile Notifications in the Health app on iPhone, you will receive notifications on Apple Watch Ultra about upcoming periods, fertile window predictions, and retrospective ovulation estimates.
On iPhone, you can also log factors in the Health app that could impact your cycle, such as pregnancy, lactation, and contraceptive use. Depending on the factors you select, your period predictions, fertile window predictions, and retrospective ovulation estimates may be turned off on iPhone and Apple Watch Ultra. For more information, see the iPhone User Guide.
Important: The Cycle Tracking app should not be used as a form of birth control. Data from the Cycle Tracking app should not be used to diagnose a health condition.