Emergency contraceptive pills taken orally twice in a row may have certain side effects, commonly withdrawal bleeding, early menstruation, delayed menstruation, and irregular vaginal bleeding, and other symptoms such as nausea, vomiting, breast tenderness, headache, dizziness, abdominal pain, and fatigue. The presence or absence of withdrawal bleeding after taking the pill is not an indication of success or failure of contraception. Although pregnancy is unlikely after taking the pill, the effectiveness of emergency contraception is not 100%. The contraceptive mechanism of the Pill is to inhibit ovulation, prevent the egg from settling, increase the consistency of the cervical mucus, increase the resistance to sperm penetration, and affect the endometrium of the uterus, thus providing a fast-acting contraceptive effect. It is important to note that after taking the pill, it is necessary to use contraception again, otherwise pregnancy is likely to occur.