The aunt's absence rules out pregnancy.

Excluding the case of pregnancy, the main reasons for menstruation do not come include the following aspects. First, multiple use of emergency contraceptives negative feedback effect, affecting the endocrine system function, resulting in menstrual disorders. Second, do curettage surgery or abortion surgery, damage to the endometrium, resulting in uterine adhesions, lack of response to the role of estrogen endometrium, can not be normal proliferation and exfoliation, resulting in menstruation does not come. The third aspect suffers from some systemic diseases, such as tuberculosis or severe anemia and hypothyroidism, which will affect the function of the ovary and uterus, resulting in irregular menstruation. The fourth aspect, excessive dieting or taking weight loss drugs, easy to affect the function of the ovary, showing symptoms of irregular menstruation.