The chance of withdrawal bleeding after taking the emergency contraceptive pill is about half or more, but there are no clinical statistics on the exact value. The emergency contraceptive pill is used within 72 hours after unprotected sex, and the earlier you take it, the better the effect. It is best to take the emergency contraceptive pill on an empty stomach for two hours before and after, as this will improve the absorption of the pill into the digestive tract and increase its effectiveness. Because the emergency contraceptive pill contains highly effective progestin, some female patients may experience endometrial abscission and withdrawal bleeding about a week after taking it. According to our clinical observation, the chance of having withdrawal bleeding is about 1/2 or more. This kind of withdrawal bleeding is usually short and the amount of bleeding is not much, but if the amount is large and lasts for a long time, you should go to the hospital promptly. The emergency contraceptive pill can only be used once in a while as a morning-after pill because it contains a lot of progestin, but it cannot be used as a long-term contraceptive.