Bustle.com on Using Period Trackers to Prevent Pregnancy:
Many people who are trying to get pregnant use period-tracking apps to figure out when they’re most fertile. But does it work the other way around? Can your period tracker act as birth control?
For those who don’t know, most period-tracking apps have you record when you get your period, then they’ll forecast when it’s going to come next, along with related predictions like how fertile you are and whether you might experience any PMS symptoms. With this wealth of information, you might be curious if you could also use your app’s data to avoid pregnancy.