Editor's note: This story was originally published on May 11, and has been updated to reflect the Supreme Court's decision of June 24 to overturn Roe v. Wade.

Period-tracking apps know a lot about you. They keep tabs on your menstrual cycles and predict fertile windows, collecting information like period length, symptoms, mood and sex drive.

Now, users with privacy concerns fear the intimate data on the apps could be used against them if they seek an abortion amid the Supreme Court's reversal of Roe v. Wade.

Striking down the 1973 landmark decision leaves abortion policy in the hands of individual states. If states criminalize abortion, the data collected by fertility and cycle monitoring apps could be used by law enforcement in investigations, experts said.

"It might seem like a kind of overstretch to say that these kinds of apps could be used to prosecute people," said Korica Simon, an associate at the Center on Privacy and Technology at Georgetown Law. "But you know, government officials are only kind of one step away from going from internet searches to going to apps to get more information about whether someone has sought an abortion."

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What are the privacy risks of period-tracking apps?

Reproductive health apps already had a spotty record regarding privacy.

Last year, the Federal Trade Commission settled with the period- and pregnancy-tracking app Flo after it shared users' data with marketing firms like Facebook and Google despite promising the information would be private.

A 2020 review by Consumer Reports found shortcomings in how five popular period tracker apps handle sensitive user data, including sharing information with marketers to target advertising.

The information stored in health apps isn't covered by the federal privacy law Health Insurance Portability and Accountability Act, so companies can legally share the data.