A child’s menstruation once every half a month may be related to the imperfect development of the gonadal secretion axis, or it may be caused by endocrine disorders, uterine pathology and other reasons. 1. Imperfect development of the gonadal secretion axis: In the first few years of menstruation, a girl’s gonadal secretion axis is still underdeveloped, the endocrine system is still immature, and her ability to regulate menstruation is weak, which is likely to cause menstrual disorders, which may result in a half-monthly menstrual cycle. 2. Endocrine disorders: some girls due to irregular work and rest, often stay up late, coupled with dietary indiscipline, overeating, eating a lot of cold and stimulating food, emotional instability, etc., may cause endocrine disorders, which may cause the girl half a month to menstruation. 3. Uterine lesions: commonly seen in uterine fibroids, endometrial polyps, etc., may lead to irregular menstruation, which may occur half a month to a menstrual situation, may also be accompanied by abdominal pain, leukorrhea and other symptoms. The child’s menstruation once every half a month may also be related to other factors, it is recommended to consult a doctor as soon as possible, after a clear diagnosis of the causative factors, to give targeted treatment and regulation.