After taking emergency contraceptive pills, most of them will have withdrawal bleeding in a week or so. This is because emergency contraceptive pills contain highly effective progesterone, which will stimulate the uterine lining, and when the drug content of the emergency contraceptive pills gradually subsides, the uterine lining will peel off and bleed, and there will be withdrawal bleeding, which is also a sign of successful contraception. However, if you take emergency contraceptive pills at different times of your menstrual cycle, the symptoms will be different, and the chances of having withdrawal bleeding are relatively higher if you take them before ovulation. If taken after ovulation, most people do not have withdrawal bleeding, but this is normal and does not mean that the contraceptive failure. Emergency contraceptive pill contraceptive efficiency is relatively high, up to about 98%, as long as in accordance with the strict oral medication, basically will not get pregnant.