The period is mostly referred to as menstruation, and it is mostly normal for a girl to not have much menstruation at the age of 11 weeks, but sometimes it may be due to uterine dysplasia, polycystic ovary syndrome and other reasons, and this situation is mostly abnormal. 1. Normal phenomenon: the age of first menstruation is usually between 13 and 14 years old, but the age of first menstruation has a tendency to advance, and it can also be at the age of 11 years old or delayed to 15 years old. At the time of menarche, the hypothalamus-pituitary-ovary axis is not fully mature, resulting in hormone level disorders in the body, which leads to the phenomenon of infrequent menstruation. 2. Abnormalities (1) Uterine dysplasia: some girls’ uterine size is obviously smaller than normal, indicating the presence of uterine dysplasia, which may also lead to delayed menarche, low menstrual flow and other symptoms. (2) polycystic ovary syndrome: some girls have the phenomenon of not having much menstruation, which may also be related to polycystic ovary syndrome, in addition to low menstruation, it may also be manifested as amenorrhea, hirsutism and other symptoms. Girls 11 weeks old menstruation is not much, it is recommended to go to the hospital in time.