Jump to navigation. Breast development is caused by hormones released by the ovaries at puberty. These hormones cause fat to accumulate, causing your breasts to enlarge. The first sign of breast development is slight swelling under the nipple, a stage of development called breast buds.
A newborn baby has nipples, areolas, and the beginnings of breast tissue, but most of breast development occurs in two different periods of time in a woman's life: first in puberty , then during pregnancy. Breast development is a vital part of puberty in the human female. Interestingly, humans are the only mammals whose breasts develop before they are needed to serve their biological purpose—breastfeeding. The first stage of breast development begins at about six weeks of fetal development with a thickening called the mammary ridge or the milk line. By six months of development, this ridge extends all the way down to the groin, but then regresses.
Here's an overview of the major physical changes girls can expect as they go through puberty:. Girls usually begin puberty between the ages of 8 and 13 years old. The earliest sign of puberty in most girls is the development of breast "buds," nickel-sized bumps under the nipple.
Breast development happens in certain stages during a woman's life: first before birth, again at puberty, and later during the childbearing years. This starts with a thickening in the chest area called the mammary ridge or milk line. By the time a baby girl is born, nipples and the beginnings of the milk-duct system have formed. The first thing to develop are lobes, or small subdivisions of breast tissue. Mammary glands develop next and consist of 15 to 24 lobes.