Breast development is a process that provides women with the tissue and structures necessary for the eventual production of life-sustaining breast milk. Typically, development begins early in life, with outward signs of change occurring during puberty. In some cases, these changes manifest during the teenage years, while in other cases, they begin substantially earlier.
Inner Development
The initial breast structure, called the mammary ridge, begins forming during fetal development, according to the Ohio State University Medical Center. In addition to externally visible nipples, female children are born with rudimentary milk ducts. When puberty begins, the ovaries begin to secrete estrogen, which in turn triggers breast enlargement through the accumulation of fat in the breasts' connective tissue. At the same time, the rudimentary duct system begins to grow, with secretory glands forming at the milk duct ends. (See References 1)
Outward Signs
In the first visible stage of prepubescent breast development, the tips of the nipples will rise up from the surrounding chest tissue, Ohio State University reports. In the next stage of development, the tissue surrounding the nipples will bud and the darkened areas of skin around the nipples---called the areolae---will begin to enlarge. In the third stage, the development of glandular tissue will trigger a further enlargement of the breasts. In the fourth stage, the nipples and areolae will typically elevate above the surrounding breast tissue. In the fifth and final stage, the breast will reach a rounded appearance and the areolas will recede in height. (See References 1)
Developmental Differences
While some girls do not experience puberty and breast enlargement until their early teens, other girls may experience these changes as early as age seven or eight, according to the Center for Young Women's Health at Children's Hospital Boston. Factors that may influence the onset of breast development and puberty include genetics, disease history, nutritional intake, body weight and levels of stress and exercise. Additionally, girls may experience a relative delay in puberty and breast development if they participate in strenuous sports such as track and gymnastics. (See References 2)
Considerations
Every girl experiences breast development at an individual pace, Children's Hospital Boston notes. In some cases, disparities in development rates may promote insecurity or uncertainty in girls. If this is the case, you may encourage them to discuss their feelings with you or another adult whom they trust. If girls show no signs of development by the age of 13, a doctor should be consulted for guidance and advice. (See References 2)
Male Breast Development
Roughly 70 percent of boys experience temporary breast development during adolescence as a result of hormonal imbalance or other causes, according to MassGeneral Hospital for Children. Typically, this development manifests as a firm, tender lump less than an inch in diameter. Temporary enlargement usually lasts for less than two years, and while your child's doctor may note this development, treatment is likely unnecessary. If male breast development occurs after adolescence, a doctor may order further diagnostic testing. (See References 3)
