Breast growth begins when a girl is as young as 7 years old and continues until she reaches maturity at the age of 17 or 18. Breasts may expand in size after this point when a woman becomes pregnant or gains additional weight in the breast area.
Breasts begin to grow as the milk glands in the breasts grow and swell. Fat cells collect around the glands as natural insulation for milk that will be produced later in the woman's life. Because fat cells are present in the breasts, the breasts will fluctuate in size as the woman's weight fluctuates. Breast growth serves the purpose of preparing the woman's body for production of milk for future children.
Development of breasts for their intended purpose is considered complete by the time a woman reaches age 17 to 18. The final size of a woman's breasts is a genetically determined factor. Girls whose mothers and grandmothers have large breasts can expect to have large breasts as well. Breasts are measured in bra sizes and range most commonly from AA to EE cup sizes, with some breasts much smaller and others much larger.
The first stage of breast growth spans from birth through childhood until the age of adolescence. During the first stage of breast growth, a girl's chest is flat and the nipples are tiny, shapeless color spots. During this stage, the breasts and chest will look the same as a boy's chest.
During the second, or budding, stage of development, the breasts begin to show signs of a small mound. At this stage, the nipples will protrude when viewed from the side. As the breasts grow in the third stage, they will become fuller and then rounder. During the second and third stages of growth, the breasts will appear pointy. Training bras are often worn at this time. During the fourth stage, the nipples and areola form and soften the pointiness of the breasts. During the last stage, the breasts fill out, become more rounded and reach full size.
Most women have one breast that is smaller than the other. In most cases, this is undetectable, but some women will develop with one breast significantly larger than the other and because of this, they will require a specially made bra so the breasts appear uniform. Other irregularities during breast growth involve the growth of abnormal nipples or fatty lumps.