The absence of menstruation for several months without pregnancy may be caused by endocrine factors, pituitary factors, ovarian factors, uterine amenorrhea, and amenorrhea caused by abnormal development of the reproductive tract. 1. Endocrine factors: women’s prolonged mental and psychological stress, psychological overstress, irregular life and diet, staying up late and so on may cause neuroendocrine disorders, which may lead to delayed menstruation, and after eliminating the above triggers, the menstrual cycle can be restored to normal. 2. Pituitary factors: such as pituitary tumors, pituitary infarction, etc., may affect the hormone level secretion in the body, which may lead to pituitary amenorrhea. 3. Ovarian factors: for example, ovarian dysfunction, premature ovarian failure or polycystic ovary syndrome can also cause delayed menstruation and may also affect the fertility of women. 4. Uterine amenorrhea: When there are abnormalities in the uterus, such as endometritis or uterine adhesions, it can affect menstrual flow and cause uterine amenorrhea. 5. Amenorrhea due to abnormal development of the reproductive tract: For example, cervical atresia, vaginal atresia, etc., due to abnormal development of the reproductive tract can lead to amenorrhea. Women who have not had menstruation for a long time and are not pregnant should pay attention to the problem and are advised to seek medical examination and treatment to avoid adverse effects.