The reasons why women have late menstruation after sex are: i. Pregnancy occurs. II. It may be a disorder of menstruation caused by high psychological stress. Third, may suffer from endometrial inflammation, pelvic inflammatory disease, so that the level of estrogen secreted by the ovaries is low and the endometrial growth is slower can also occur delayed menstruation. When a woman has delayed menstruation after sex, she needs to go to the hospital for gynecological ultrasound and chorionic gonadotropin level check, and amenorrhea will occur if pregnancy has occurred. If pregnancy does not occur, sex hormone levels need to be tested. If there is no abnormality in the uterine cavity under ultrasound and the endometrial lining is growing thick, progesterone can be given to promote menstruation. If the sex hormone level is low after the test, estrogen and progesterone drugs need to be given to treat the cycle.