Breast development in 15-year-old girls. Breast development is affected by heredity, nutritional status, external environment, medical means, physical fitness and other factors, and the time when breast development begins as well as the time when it ends varies from girl to girl. According to the general development situation, most girls’ breasts start to develop after the age of 8 and before the age of 13, with the duration of development ranging from 3-5 years, and full maturity is usually between the ages of 14 and 18. The size of a girl’s breasts is closely related to her body weight, and according to the general situation of teenage girls in China, the bust size of a 15-year-old girl is generally between 80-92cm, so as long as the size of the breasts is in harmony with the body and is not too different from most girls of the same age, there is no need to worry. But 15 years old still flat or huge breasts should pay attention to, because it may be disease factors caused by abnormal breast development, we must pay attention to their own breasts. 15 years old girls breasts have formed the adult female breast size of the scale, but not as adult female breasts so plump and firm.