Emergency contraceptive pills are generally not harmful to the body when taken only once. Although the emergency contraceptive pill is a highly effective hormone, it is safe to take it no more than three times in a year, and at most once a month, and generally does not cause endocrine disruption and disrupt menstruation. However, the contraceptive rate of emergency contraceptive pills is not 100%, and all emergency contraceptive pills have a 2%-4% chance of unintended pregnancy. Also, emergency contraceptives may disturb the peristalsis of the fallopian tubes, which may cause localized fertilization of the egg in the fallopian tubes and may lead to ectopic pregnancy. Therefore, if you experience delayed menstruation after taking the emergency contraceptive pill, or if you experience a small amount of vaginal bleeding until your period, you should first consider the possibility of pregnancy, and a blood or urine HCG test is needed to rule it out.