The main reason for vaginal bleeding after taking the emergency contraceptive pill is that the pill is a high potency progestin. When the pill is stopped, the endometrium is deprived of this exogenous hormonal support and withdrawal bleeding will occur. The clinical manifestation is a small amount of vaginal bleeding, which stops on its own in about 3-5 days, and most of them have no other clinical symptoms. This is the reason for bleeding from oral emergency contraceptives. When the pill is taken during the second half of the menstrual period, there are relatively few cases of withdrawal bleeding, so there is no need to be nervous as this is a side effect of the pill.