Although not a common side effect, the hormones in the pills (either
progestin alone or
progestin combined with
estrogen) can cause some women to bleed at unexpected times. If that is the cause of your bleeding, it is not dangerous and you should expect it to go away by itself after you get your next period.You should know, however, that your unusual bleeding could be caused by something else that, in rare cases, may be more serious.