Hypomenorrhea refers to normal menstrual cycle, but the number of days of menstruation is shorter than 2-3 days, the volume of menstruation is low, and the blood is dark purple or pink. The causes of menorrhagia are: 1. Hypothalamus and pituitary gland hypofunction: mostly due to mental factors, genetic or environmental factors, but also due to systemic diseases or long-term use of contraceptives. Due to the above factors inhibit the pituitary gland to promote the secretion of glandular hormones and lead to menorrhagia. It can also be seen in congenital uterine dysplasia, as the uterus is very small, only a very small amount of endometrium is shed, and the menstrual volume is low. Shandong Qianfo Mountain Hospital Obstetrics and Gynecology Department Lv Hongtao 2, some gynecological diseases are common causes of menstruation: such as endometrial tuberculosis destroyed part or all of the endometrium to form a scar, and lead to menorrhagia or even amenorrhea. 3, scraping surgery: especially after multiple abortions scraping surgery, due to excessive mechanical damage, resulting in the endometrium can not repair regeneration, or uterine cavity adhesions, can occur menorrhagia or even amenorrhea. 4, ovarian insufficiency: In the endometrial cells, there is a special type of particles called lysosomes, which are related to the amount of menstrual blood and bleeding time. If the level of estrogen and progesterone is high, there will be more lysosomal complexes, more bleeding and longer bleeding time. On the contrary, if the ovaries are underdeveloped and the amount of sex hormones is low, there will be less lysosomal complexes, less bleeding and shorter bleeding time. All of these reasons may lead to conception. In some women, the menstrual flow has been low since the first menstruation, but the menstrual cycle and ovulation are normal, which does not affect conception.