The morning-after pill usually refers to the emergency contraceptive pill and is recommended to be taken within 72 hours after sexual intercourse, the sooner it is taken the more effective it is. The emergency contraceptive pill is a highly effective progestogen that inhibits ovulation, prevents fertilization of the egg and increases the viscosity of cervical mucus, thus achieving contraceptive effects. It can be used after unprotected intercourse, or when contraception fails such as when a condom accidentally breaks or slips. Emergency contraceptive pills need to be taken within 72 hours after sexual intercourse and are only effective for this sexual intercourse, but the effectiveness rate is not 100%, usually above 90%. It should be noted that the use of emergency contraceptive pill should not exceed 2 times in 1 month and 3 times in 1 year to avoid endocrine disorders, menstrual disorders and even amenorrhea in serious cases, so it is not recommended as a regular contraceptive method.