Breast Development

Breast development is a natural process that occurs in girls during puberty. It involves the growth of your mammary glands, which produce milk after you have a baby. Puberty is a time when your body begins to grow and change. Breasts are often one of the first changes you may notice.

Every girl’s breasts grow differently. One breast may grow faster than the other. Size and shape can vary a lot between people. Breast size and shape are mostly controlled by hormones. But genetics, body weight and other factors can all affect how your breasts develop.

What is the normal age for breast development?

Most girls start developing breasts between the ages of 8 and 13. This is about the time puberty starts.

If your breasts begin to grow before age 8, or there aren’t any signs of growth by age 13, it’s a good idea to talk to your healthcare provider. Early or late development is sometimes normal. But your provider can check to make sure your development is on track.

What is the first sign of breast development?

The first sign of breast development is the appearance of small breast “buds.” These are nickel-sized bumps under your nipples and areolas. Your areolas are the small circles of skin that surround your nipples. It’s common for one breast to begin developing before the other, and the growth may be uneven. The buds can sometimes feel tender or sore.

These early changes are completely normal. They typically improve over time as development continues. Breast budding usually marks the beginning of puberty. Other changes — like growth of pubic hair, hip widening and eventually, the start of menstrual periods — will follow.

What makes breasts grow?

Breast growth happens because of hormones. Estrogen is the main hormone that tells your breasts to grow. It signals your mammary glands and surrounding connective tissue to get bigger. Later in puberty, a hormone called progesterone also helps your breasts develop fully. These hormones change throughout the month. That’s why your breasts may sometimes feel sore, tender or itchy, especially before your period.

How do breasts develop?

Breast growth happens in stages as hormones signal your body to grow breast cells. These changes can look and feel different for everyone. But it typically happens in steps. Healthcare providers often describe these steps using the Tanner stages of breast development. The Tanner scale breaks breast development into five stages.

The breast development stages are:

• Tanner stage 1: This is before puberty starts. There’s no development yet. Your chest is flat, with only slightly raised nipples.
• Tanner stage 2: This stage is when breast budding occurs. It’s called thelarche. Your breast buds may feel sore or tender as they begin to grow. Your nipples and the skin around them (areolas) may get larger or more raised.
• Tanner stage 3: Your breasts become rounder as milk-producing glands and fatty tissue grow. Your areolas continue to get bigger and may darken. Your nipples may start to stick out more.
• Tanner stage 4: You’ll notice areola and nipple changes in this stage. They’ll form small mounds on top of your breasts. Your breasts will look fuller. But they aren’t fully mature yet. You may experience swelling or tenderness.
• Tanner stage 5: Your breasts reach their mature size and shape. But one may still be larger than the other. Your areolas usually flatten back into the curve of your breasts, with only the nipples raised.

Periods usually begin two years after breast buds start developing. If you haven’t started your period as you’re heading toward year three, talk to your pediatrician. They may refer you to a doctor who specializes in problems of puberty (an adolescent medicine doctor).

When does breast development stop?

Breast development continues through the stages of puberty. It’s usually complete by about the age of 17. By the end of puberty, your breasts should reach their adult size and shape.

What changes happen to breasts during your menstrual cycle?

Once your periods begin, you may notice your breasts change during your cycle. They can feel tender, swollen or heavier before and during your period. These changes are normal. They happen because your hormones rise and fall throughout the month. That’s why it’s called a menstrual cycle.

What happens to your breasts later in life?

Your breasts will continue to change even after puberty. They may grow larger, feel fuller or change shape during pregnancy and breastfeeding. Later in life, during menopause, hormone changes can make breasts feel softer or smaller.