The first day of bleeding is the beginning of the menstrual cycle, and the interval between the first day of two menstrual periods is called the menstrual cycle, so the calculation of the menstrual cycle should include the time of menstrual flow. Some women only count the time when their menstruation clears, so they may think that their menstrual cycle is shortened. Clinically, some women often complain of abnormal menstruation and have menstrual flow twice a month. In fact, if you count carefully, it is normal to have one period at the beginning and one at the end of the month. The normal menstrual cycle is 28-35 days, the length of the cycle can vary from person to person, 7-10 days ahead or behind can be regarded as the normal range, as long as you can maintain a certain regularity can not be considered as menstrual disorders. There are many reasons for long menstrual cycles, including genetic problems, endocrine problems and immune problems, as well as psycho-neurological factors, tumors, trauma and medications that can cause sporadic menstruation. It is important to go to the hospital for examination to identify the possible causes and to treat them as much as possible in order to achieve better results. Also, irregular menstruation can have an impact on fertility, so it is important to seek medical attention as soon as possible if there is a problem. There are many factors that can cause a long menstrual cycle, which can be divided into the following categories: 1, central nervous system – hypothalamus abnormalities, including mental stress, such as environmental changes, excessive tension and mental shock caused by mental stress; weight loss, excessive exercise, anorexia nervosa, drugs and so on caused by the hypothalamus to secrete gonadotropin regulation dysfunction or inhibition; in addition, there are congenital diseases or brain developmental malformations. In addition, there are also congenital diseases or abnormalities of brain development and tumors that lead to abnormal hormone secretion. Pituitary abnormalities refer to the abnormal secretion of gonadotropins due to pituitary lesions, both congenital and acquired, such as pituitary tumors. 3, ovarian abnormalities Due to congenital dysplasia of the ovaries, abnormal ovarian function or secondary lesions resulting in abnormal menstruation, such as polycystic ovary syndrome, clinical manifestations of menstrual sporadic, irregular, hirsute, obese, etc.; ovarian functional cysts, ovarian tumors and other hormonal changes can also affect menstruation; and serious pelvic infection, can make bilateral ovarian tissue destruction, thus affecting menstruation. This can affect menstruation and can even lead to permanent amenorrhea, with tuberculosis being the most common. 4. Uterine abnormalities Uterine dysplasia and destruction of the endometrium can also cause sporadic menstruation and even amenorrhea. Endometrial destruction includes inflammatory factors, such as endometrial tuberculosis; it can also occur after childbirth or after abortion due to excessive scraping resulting in damage to the endometrial basal layer or adhesions, etc.