Welcome to the Fitbit Community @od_ile, it's nice to have a new member around! We're always interested in ways to improve the product and see what we can implement based on the feedback received from you guys. So, please make sure to also add these comments in the feature suggestion Toggle switch ON/OFF predictions for Ovulation & Fertility Window.
As you may know, the predictions for your period, fertile window, and ovulation day are estimated using an algorithm that includes the period and cycle length information you provide. If you don’t provide some of the information about your cycle, Fitbit uses a 28-day cycle and 5-day period as a starting point for estimations. Your fertile window is always shown as 7 days in the Fitbit app. For more information, see What is a fertile window and ovulation?
Period and fertile window predictions become more personalized as you log your period consistently.
You can edit the average cycle length and period length you provided during setup; however, these settings only affect your initial predictions.
Let me know if there's anything else I might assist you in the meantime.
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