How to Use Clue

Why we are removing the fertile window

Changes to the Clue app

Top things to know:

  • Variability in your cycle makes it difficult to predict the fertile window accurately based on how we previously calculated it

  • The fertile window in the Clue app could have been inaccurate, and in particular, too short for safety for those using it to avoid pregnancy - this feature was never intended as birth control

  • Users who want to use Clue to become pregnant can still use the predicted day of ovulation

If you’ve been using the Clue app for some time, you may have noticed a part of your cycle labeled the “fertile window.” Your biological fertile window consists of the days leading up to, and including, the day of ovulation.

The fertile window in the Clue app was an approximation that didn’t account for the variability of each person’s cycle. Because there is too much variation from one person to another, and from cycle to cycle, we determined that it could be misleading to those who wish to use the fertile window to avoid pregnancy. Using the Clue fertile window to avoid getting pregnant involves an unknown, and therefore unacceptable, risk of unintended pregnancy. We hope to offer a solution to this problem in the near future, but in the meantime, we have removed the estimated “fertile window” from the Clue app.

For those interested in using Clue to become pregnant, the predicted ovulation day can serve as a way for people to get a better understanding of their fertility. This is still an approximation, as the day of ovulation is very difficult to predict; peak fertility varies considerably even among people with predictable cycles. 

At Clue we aim to be the best data-driven and evidence-based period tracker out there. As the nature of data and technology is always changing, we feel it’s our responsibility to stay up to date on our features and health information. We regularly audit and update our features and product information so that all users can benefit from and feel safe using our app and content. Our commitment to you is to be honest, and not to over-promise.

Track your cycle in Clue.

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