It is not normal for girls to develop breasts at the age of 10 weeks, but it is normal for girls to start developing secondary sexual characteristics at the age of 11 weeks, that is, to start growing breasts. If the breasts develop at the age of 10 weeks, the clinical diagnosis is early sexual development. If a girl has early sexual development, she should have her left wrist orthopantomogram, which is a test of her bone age, to clarify the difference between her actual height and her height based on her bone age. The goal of treatment for early sexual development and precocious puberty is to increase the child’s lifetime height as an adult. If the actual height of the child differs a lot from the calculated height based on bone age and is much shorter, further examination, the etiology of the child’s premature sexual development, and related tests for growth hormone, thyroid hormone, and sex hormones are required. Actively give the child treatment to avoid the child being too short in height for life in the future.