Women using period tracking apps face “real and frightening privacy and safety risks”, according to a new report from the University of Cambridge’s Minderoo Centre for Technology and Democracy.

The researchers say the apps, which have surpassed 250 million global downloads across their top three providers, collect extensive personal data – including information on users’ exercise, diet, medication, sexual preferences, hormone levels and contraception use – that can be “sold at scale” and used for consumer profiling.

“There are real and frightening privacy and safety risks to women as a result of the commodification of the data collected by cycle tracking app companies,” said Dr Stefanie Felsberger, lead author of the report.

The findings describe period tracker apps (or CTAs) as a “lucrative business” due to their access to “extremely valuable and fine-grained user data”. The report warns that the commercial value of this data often results in it being shared with an “inextricable net of third parties”, leaving users vulnerable to targeted advertising, data exploitation, and potential harm.

“CTA data is not only commercially valuable and shared with an inextricable net of third parties (thereby making intimate user information exploitable for targeted advertising), but it also poses severe security risks for users,” the report states.

The researchers highlight how many women begin using these apps when trying to get pregnant, triggering changes in their shopping habits. This behaviour shift has made reproductive intent one of the “most sought-after” categories in digital marketing.

“Data on who is pregnant, and who wants to be, has therefore emerged as some of the most sought-after information in digital advertising,” the researchers said.

Beyond advertising, the report warns that menstrual data could be misused in other contexts – including health insurance discrimination, impacts on employment opportunities, or even domestic abuse, should the data fall into the wrong hands.

Calling for improved oversight of the femtech sector, the authors recommend enhanced data security, meaningful consent options within apps, and for public health bodies like the NHS to create non-commercial alternatives for cycle tracking.

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“Menstrual cycle tracking apps are presented as empowering women and addressing the gender health gap,” said Dr Felsberger. “Yet the business model behind their services rests on commercial use, selling user data and insights to third parties for profit.”

Professor Gina Neff, executive director of the Minderoo Centre, echoed the call for reform: “The use of cycle tracking apps is at an all-time high. Women deserve better than to have their menstrual tracking data treated as consumer data, but there is a different possible future.”