After taking the emergency contraceptive pill, if you have sex again, you need to take contraceptive measures. This is because the emergency contraceptive pill only has a preventive effect on the previous sex, and its mechanism is to prevent or delay ovulation, that is, when there is sex when there is ovulation, after taking the pill, the progesterone of the pill will interfere with the level of hormones secreted by the ovaries, so it can prevent the ovaries from discharging eggs and prevent pregnancy, This prevents pregnancy. In addition, it can interfere with the fertilization of the egg, that is, if ovulation has already occurred at the time of sex, the fertilized egg cannot be fertilized due to changes in the endometrium after taking the pill. However, the pill will be excreted through urine after it is taken into the body, so it only has a contraceptive effect on the first time, but not on the second. If you have sex again, be sure to take birth control measures.