The term “vacation” generally refers to menstruation. A twelve year old girl’s period used to be normal and this month’s delay may be due to the body’s hormone level fluctuation, abnormal ovarian function and pregnancy. 1. Hormone level fluctuations: twelve-year-old girl’s menstrual delay of about seven days is generally a normal physiological phenomenon, may be due to life stress, work and rest habits, and other reasons lead to recent hormone level fluctuations in the body, which in turn caused the prolongation of menstruation. 2. Abnormal ovarian function: twelve-year-old girl in this stage of development ovarian function is not yet fully developed, and then the endometrium can not achieve regular shedding, there may be menstrual disorders, menstrual disorders, the situation. 3. pregnancy: twelve-year-old girls after menarche is proof of fertility, menstruation delay for a longer period of time may also be due to pregnancy. Therefore, the twelve-year-old girl menstruation before normal this month delay may also have other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.