The reaction of emergency contraceptive pill is different for everyone, a few people will have gastrointestinal discomfort, abdominal bloating and other symptoms, some people will have a short period of menstrual changes, some have breast swelling and pain, and some women take emergency contraceptive pills have no reaction at all, a small number of people can fail to contraception. 1. Gastrointestinal symptoms and bloating: some patients will have gastrointestinal irritation when taking emergency contraceptive pills, resulting in nausea and vomiting, and some patients will feel bloated, which does not mean that they are pregnant. 2. Menstrual changes: taking emergency contraceptive pills is relatively early before ovulation, the chance of withdrawal bleeding will be greater, some are simply early menstruation can be naturally clean, but also some women will have bleeding, most do not need special treatment. 3. breast swelling and pain: emergency contraceptive pills belong to a relatively large dose of progesterone, many patients after taking the drug will lead to breast swelling and pain symptoms or aggravation, generally can be observed after stopping the drug for a week after the symptoms, especially after menstruation can be automatically relieved basically nothing, you can do a mammography. 4. No reaction: some women will not have any reaction to the emergency contraceptive pill, and it will not affect the original menstrual situation. 5. Contraceptive failure: some patients are emergency contraceptive pills can not achieve the purpose of contraception, may fail to get pregnant, so if the menstrual delay, or menstrual flow is reduced, can not be a normal flow of the situation should be checked as soon as possible, in particular, to be vigilant about ectopic pregnancy.