In the United States, African-American girls on average enter puberty earlier than girls of other ethnicities-approximately 15 percent of all 7-year-old African-American girls, begin the first phase of breast development.
Breast development in many pubescent girls begins anytime between the ages of 7 and 13. The start of breast growth is frequently the first physical marker of the onset of puberty. (If a girl is overweight, it may look as if her breasts are budding, but this might not be the case.)
The first indication of adult female breast development is the enlargement and possible darkening of the areola around each nipple. Minimal discomfort or tenderness around the breast area is common, but it customarily disappears after a few months or so. This tenderness is caused by the influx of hormones that occur in early puberty. The accelerated growth of the breast tissue stretches the skin, often causing this area to itch. Scarring in the form of stretch marks may be visible.
Both breasts may not develop at an equal pace, and one will often get a head start on the other. Breast growth starts one to two years before menarche and continues for approximately four more years.
In stages, breast development typically progresses as follows:
- Stage 1: Breast development is absent in the prepubescent girl.
- Stage 2: Nipples become bigger and area around the breast is frequently tender. The breasts are beginning to bud.
- Stage 3: Around the time of a girl's first menstrual period or menarche, milk glands, ducts and fat tissue form inside the breast.
- Stage 4: Nipples are now prominent and breasts are almost their full size and begin to change in shape.
- Stage 5: Around 18 years of age, the full and final stage of breast development is completed.