In the United States, African-American girls on average reach puberty sooner than girls of other ethnicities -- among 7-year-old African American girls, around 15 percent have begun the first stages of breast development [source: Durso].
Breast Development in Pubescent Girls
Breast development in most girls begins between the ages of 7 and 13. It's often the first physical marker of the onset of puberty. (If a girl is overweight, it may appear that her breasts have begun budding when this isn't the case.)
The first sign of adult breast development is an enlargement and possible darkening of the areola around each nipple. Slight discomfort or tenderness in the breast area isn't uncommon, but it goes away after a few months or so. This tenderness is caused by the influx of hormones that occurs in early puberty. The rapid growth in the breast area will stretch the skin, often causing the area to itch. Scarring in the form of stretch marks can occur.
Both breasts may not develop at an equal rate, and one will often begin before the other. Breast growth occurs one to two years before menarche and continues for about four years after it.
In stages, breast growth tends to advance as follows:
- Stage 1: There is no breast development on the prepubescent girl.
- Stage 2: Nipples become larger and breast area is often tender. This is the initial budding of breasts.
- Stage 3: This is around the time of menarche. Milk glands, ducts and fat tissue are developing inside the breast.
- Stage 4: Breasts have nearly reached their full size will now change in shape. The nipples will protrude.
- Stage 5: This occurs around 18 years of age, and represents the full and final stage of breast development.