There is no one to take the emergency contraceptive pill is not useful answer is yes, resulting in contraceptive failure for the following reasons: 1, although the emergency contraceptive pill is a better contraceptive pill, but not 100% can achieve the purpose of contraception, there are very few people may eat after not good contraception, but its probability is very low. 2, some people eat the drug after the gastrointestinal reaction is more serious, nausea, vomiting, so that part of the 3, some people do not have a good grasp of the time to take the pill, the emergency contraceptive pill should be taken within 72 hours after intercourse, the earlier you take the better the contraceptive effect. 4, some people still have sex after taking the pill, but no contraceptive measures will also lead to contraceptive failure, because the emergency contraceptive pill only to take the pill within 72 hours before Sexual life has a contraceptive effect.