If vaginal bleeding occurs after 3 days of taking the emergency contraceptive pill, it is mainly because the emergency contraceptive pill is a progestin, which will cause the endometrium to thicken abnormally after taking the pill, and after stopping the pill, the endometrium loses the support of the progestin, and so retractive bleeding will occur. This kind of bleeding is often small in amount and is not accompanied by other symptoms, and it will clear up on its own in about 3 days. If you are taking short-acting contraceptive pills and bleeding occurs during the period of taking the pills, it is mainly because the main components of short-acting contraceptive pills are oestrogen and progesterone. After taking short-acting contraceptive pills containing oestrogen and progesterone, it may lead to irregular vaginal bleeding, which is a side effect of the drug itself. It is also recommended to change sanitary napkins regularly during the bleeding period and keep the vulva locally clean.