There are several conditions that lead to the absence of menstruation: i. When a woman is pregnant, her menstruation will stop and she will not have a period. Second, when women have endocrine disorders, such as high mental and psychological stress or environmental changes, frightening and over-stimulating factors, which imbalance the level of estrogen and progesterone secreted by the ovaries, it will lead to the absence of menstruation. Third, women suffering from certain diseases, such as uterine adhesions, premature ovarian failure, pituitary tumors, etc., can also lead to amenorrhea. Fourth, women taking certain drugs that inhibit ovulation, such as progesterone drugs, or drugs for thyroid function, anti-tumor drugs, and drugs for pituitary tumors, can also lead to amenorrhea. Therefore, when amenorrhea occurs in women, it is important to actively look for the cause and use the corresponding treatment as soon as possible.