Natural Breast Growth

One of the most conspicuous physical events in a girl's life is the development of her breasts. During this time, her body undergoes other physical changes, preparing her for childbearing. Girls mature at different rates, and one girl may develop breasts in elementary school while another girl's breasts may begin to grow a few years later. Understanding what's happening to your body can make the transition more comfortable.

Early Stage Breast Growth

Outward signs of breast growth begin when a girl nears puberty and it continues until her breasts reach their adult size, usually by the time she's 18. Approximately two years before she gets her first menstrual period, a girl develops breast buds and raised nipples, according to the "Gale Encyclopedia of Children's Health." Soon after, the pigmented skin surrounding the nipple, called the areola, widens and fat tissue begins to develop beneath the center of the breast.

Continued Growth

Breast growth continues as glandular breast tissue develops, first in a conical shape but later spreading to the outer areas of the breasts, forming rounded mounds. At this time, the color of the nipples may darken and the nipples may become larger. Some girls, but not all, according to the "Gale Encyclopedia," will develop a secondary, enlarged nipple tip during this stage. Breast growth now slows as the breasts near their final adult size.

Time Line

Between the ages of eight and 13, most girls experience the beginning of breast growth. Approximately five years passes from the start of early breast growth until the breast reaches the adult stage, although in some females the process is slower, lasting up to 10 years. Despite reaching adulthood, complete breast growth and development does not occur unless the female becomes pregnant, triggering the final hormonal growth period, the "Gale Encyclopedia" states.

Monthly Changes

Monthly swelling in the days before the onset of a girl's menstrual period may make her breasts feel larger as her body prepares for a possible pregnancy. Her body releases estrogen just before ovulation, which occurs in the middle of her cycle. After ovulation, her body releases progesterone, which stimulates the temporary growth of her milk glands. If she is not pregnant, her breasts will return to their normal size after her period starts.

Different Breast Sizes

It's not unusual to have different size breasts, according to TeenGrowth.com. This frequently occurs during puberty and ongoing breast growth, but it may also last into adulthood. Unless one breast is growing much more quickly than the other one is, there's probably no reason for concern.

Breast Growth During Pregnancy

At approximately the eighth week of pregnancy, a woman's breasts begin to grow in anticipation of childbirth and breastfeeding. According to BabyCenter.com, they will continue to grow, often by as much as two cup sizes, during the woman's pregnancy. Blood flow increases to the breasts and the milk glands develop and become larger. Some women experience soreness or tenderness during this time.