What is the normal process of breast development?

Updated: May 03, 2021
  • Author: Harsh Grewal, MD, FACS, FAAP; Chief Editor: Robert K Minkes, MD, PhD  more...
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During the sixth week of development, the mammary glands first develop as solid downgrowths of the epidermis that extend into the mesenchyme from the axilla to the inguinal regions. Later, these ridges (ie, milk lines) disappear, except in the pectoral area. The nipple forms during the perinatal period with the proliferation of the mesenchyme underlying the areola.

At birth, the nipples are poorly formed and are often depressed. Soon after birth, the nipples are raised from the shallow mammary pits by proliferation of the surrounding connective tissue.

Breast development

Budding of the breasts, or thelarche, usually occurs at approximately age 10-11 years in females. This developmental change, along with adrenarche (ie, appearance of dark hair over the mons veneris), signifies entry into Tanner stage II of development. From this stage, complete maturation to Tanner stage V usually takes more than 4 years. Breast maturation can take place over a period as short as 18 months or as long as 9 years.

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