The first reason for not having menstrual periods is to rule out the possibility of pregnancy. Secondly, it may be due to endometrial damage, ovarian dysfunction, ovulation abnormality, polycystic ovary syndrome, hypothalamic amenorrhea, or other reasons, which need to be consulted in time. 1. Pregnancy, if a woman has normal sexual life without contraception, the absence of menstruation should be considered as a possibility of pregnancy. 2. Damage to the lining of the uterus can lead to menstrual failure, such as hysteroscopic surgery and abortion. 3. When ovarian function declines, ovulation often does not occur, which can lead to the absence of menstruation. 4. Patients with polycystic ovary syndrome mainly manifest amenorrhea, obesity, etc., and it is difficult to ovulate, which can lead to the absence of menstruation. 5. Weight loss or mental shock can lead to hypothalamic amenorrhea, inhibiting the hypothalamic-pituitary-ovarian axis, causing disruption of the body’s endocrine system, which may lead to menstruation.