Period-tracking apps have been accused of sharing private data with Facebook, including the details of when users have had sex.
Rights charity Privacy International has studied a range of period-tracking apps (popular with people trying to get pregnant) to see what data was shared with Facebook.
The apps can collect highly private data including what contraception women use, what sanitary products are used and when people have sex.
Privacy International found that some apps were sharing this data with Facebook - and in the wake of the investigation, at least one has changed its policies.
Many popular period apps don’t share data, but several including Maya by Plackal Tech, MIA by Mobapp Development Limited and My Period Tracker by Linchpin Health shared information.
Privacy International said, ‘The wide reach of the apps that our research has looked at might mean that intimate details of the private lives of millions of users across the world are shared with Facebook and other third parties without those users' free unambiguous and informed or explicit consent, in the case of sensitive personal data, such as data relating to a user's health or sex life.’
Maya said that it had removed Facebook’s ad-tracking tools from its app, and the changes would come into effect immediately.