Many women use various period tracking apps to help them  monster their monthly cycles. These apps record  highly intimate information about these women, not merely when their period is due, but information about their sex lives, whether or not they want to have a baby, their moods, if they have unprotected sex, and about their general health.

Many of these apps  integrate Facebook’s Software Developer Kit (SDK) which allows Facebook to harvest this data and then pass it on to their extensive advertising network and third party analytics network.

Read More: Mashable