If a woman has intercourse, she will not get pregnant if she has a normal menstrual period. Women’s menstrual cycle is mainly due to the luteal atrophy before menstruation, estrogen and progesterone levels drop, the endometrium loses the support of high hormone levels to exfoliate and bleed. After pregnancy, blood progesterone and estrogen levels will be higher and show a continuous rise, so women will not have menstrual flow due to the decline in hormone levels. In addition women after intercourse, to menstruation vaginal bleeding, but also contains two special cases, is a woman in the state of pregnancy bleeding. After the patient is pregnant, due to various circumstances, the embryo bed abnormal ectopic pregnancy or abnormal embryo development, and the occurrence of preeclampsia, vaginal bleeding can occur. Individuals who experience cyclic vaginal bleeding after pregnancy, similar to menstruation, but with no abnormal development of the fetus and no abnormalities on examination, are called “stimulated menstruation” in Chinese medicine.