A 7-year-old baby girl has abnormal breast development on one side. It is mostly caused by pathological factors, such as precocious puberty. The 7-year-old female child will have precocious puberty due to the large secretion of sex hormones in the body, and there will be the appearance of secondary sexual characteristics, which can be manifested in the development of one side of the breasts. The early secretion of sex hormone will affect the secretion of growth hormone, resulting in growth and developmental disorders in 7-year-old girls. You can go to the hospital for hormone test and adjust as soon as possible. There are many other reasons for the abnormal development of one side of the breasts of a 7-year-old baby girl, and it is recommended to go to the hospital in time for examination and treatment, so as not to affect the physical health of the baby girl.