If a woman takes emergency contraceptive pills during ovulation, the chance of pregnancy is still relatively low, mainly because emergency contraceptive pills have two contraceptive mechanisms: one, can inhibit ovarian ovulation, although the emergency contraceptive pills during ovulation, may have already finished ovarian ovulation, inhibit ovarian ovulation of the efficacy of the role of the corresponding role. Second, the emergency contraceptive pill will also make the endometrium abnormal thickening, after taking the fertilized egg will have no way to implant in the abnormal thickening of the endometrium, but also play a role in contraception, so in the ovulation period to eat emergency contraceptive pill will still play a corresponding contraceptive effect. Regardless of which period to take emergency contraceptive pills, the contraceptive effect can not reach 100%, this point should also be noted.