Three days after intercourse, if there is a normal menstrual period, the patient will not be pregnant. First of all, if menstruation comes three days after coitus, it proves that the patient’s coitus time is within the safe period, and the patient does not have ovulation disorders, and no ovulation occurs within the safe period. In this case, the patient has no eggs, only sperm, and will not get pregnant. Secondly the sperm that enters the patient’s uterine cavity and fallopian tubes can only survive for a maximum of 72 hours. Sperm in the uterine cavity will be flushed out of the woman’s uterine cavity and vagina as the endometrial lining peels off and menstrual blood travels down. Sperm localized in the fallopian tube will be absorbed locally after death. So the patient will not get pregnant three days after intercourse, as long as there is a normal menstrual period, and the sperm cannot be maintained until the next month of ovulation.