In the process of love, wearing a condom accident, or a moment of “sex”, simply did not take any contraceptive measures, after the fact, women will often take emergency contraceptive pills to avoid pregnancy. So, how long does it take for emergency contraceptive pills to be effective? On the effectiveness of emergency contraceptive pills, these four points to know: 1, should be taken within 72 hours, the earlier the better After an unprotected sex, within 72 hours (preferably within 12 hours) to take the drug is effective, and during this period, the earlier the time to take the drug, the better, otherwise it will be due to the delay in the time of the medication and lead to a decline in the efficacy of emergency contraception. The sooner the pill is taken, the more effective it is, otherwise it will be less effective because of the delay in its administration. The overall contraceptive success rate of the emergency contraceptive pill is about 85%. 2, after taking the pill, after 12 hours to make up for taking a better effect in unprotected sex within 72 hours after taking the pill, half an hour can be effective, after 12 hours to make up for taking a pill. It is absolutely ineffective to take 1 pill right after the next sexual intercourse, and it is also ineffective to repeat it before menstruation. Because the emergency contraceptive pill only delay ovulation, and can not completely inhibit ovulation. 3, after taking the pill, and only the most recent unprotected sex effective emergency contraceptive pill and only the most recent unprotected sex before taking the pill to produce contraceptive effect, and will not always maintain the contraceptive effect. If the user has unprotected sex again after taking the emergency contraceptive pill, she may still get pregnant. 4, repeated use of emergency contraceptive pills, the effect is poor, side effects increased significantly Emergency contraceptive pills contain a large number of hormones, side effects. If in the same menstrual cycle, multiple use of emergency contraceptive pills, in addition to the poor effect, will also make the side effects of the drug increased significantly. It is recommended that it be used no more than once in a month and no more than three times in a year. Warm tips: 1, the emergency contraceptive pill side effects are relatively large, easy to cause endocrine disorders, menstrual disorders and even amenorrhea in women, can not be used indiscriminately. 2, emergency contraceptive pills can not be used as a regular contraceptive method, just a kind of after the fact remedial way, and often will not be reliable. If there is a need for contraception, you can use other scientific contraceptive methods such as wearing a condom or taking oral short-acting contraceptives. 3, women should pay close attention to the changes of menstruation after using the pill, especially when the expected menstruation is delayed for more than 1 week, they should go to the hospital for examination in order to clarify whether they are pregnant or not, and pay attention to exclude ectopic pregnancy. 4. After the failure of emergency contraception, one can choose to continue the pregnancy without harming the fetus. References: [1] Ma Peiqi, Development and selection of emergency contraceptive pills. Shanghai Medicine, 2013,34(3):52-54. [2]Cheng Linan,Safety of emergency contraceptive pills. Journal of practical obstetrics and gynecology[R],2014,30(7):488-490.