Everything You Need to Know About Breast Development During Puberty

For children assigned female at birth, the first sign of puberty is usually the development of breasts. While this milestone can be exciting, it can also be filled with many concerns—for both kids and their parents.

Here, we answer your top questions about the stages of breast development, including an expected timeline and signs that your breasts are growing. Keep in mind that everyone develops at a different rate, and you should bring up any concerns with your child's health care provider.

When Do Breasts Begin Developing?

There's a fairly wide range of "normal" when it comes to the age that preteens start developing breasts, says Lisa Hoang, MD, a pediatrician with Providence Mission Hospital in Southern California. The most common time for this to happen is between the ages of 10 and 11. But breast development can start as early as 7 or 8 years old.

Parents whose children develop breasts on the early side may be taken aback, says Dr. Hoang, but it's important to reassure your child that what's happening is natural and normal. "Start talking to your child about what to expect with puberty and allow them to ask questions about it," advises Dr. Hoang. "Reassure your child that it's all a normal part of development and help to cultivate a positive body image."

Typically, about 2.5 years after breast development begins, a child will experience their first menstrual period, says Dr. Hoang. There's also a wide time frame for menarche (first period), but the average age is around 12 years old. Other signs of puberty will be present as well, including increased body hair, pubic hair, and vaginal discharge.

For most teens, breast development will be complete by 17 or 18 years old, says Dr. Hoang. That said, some people will continue to develop into their early 20s. Breast changes can also occur during other life stages, such as pregnancy.

Signs Your Breasts Are Growing

As your child's breasts develop, they can experience a few notable symptoms, says Traci Brooks, MD, chief of pediatrics at Cambridge Health Alliance. Symptoms might include the following.

• As breast tissues grows and the nipple pushes out, your child may experience some tenderness
• Itching, tingling, and some irritation may occur as the breast skin stretches
• Some teens experience pain and discomfort while running, playing sports, or engaging in other physical activities

Note that these signs of breast growth are normal, and they usually subside with time.

Is It Normal For Breasts To Be Uneven?

We think of the body as developing in a symmetrical manner, but that's not always the case, says Dr. Brooks, and breasts are no exception. This means it's completely normal if your teen's breasts aren't evenly sized. It's common for one breast to be larger than the other and for each breast to have a slightly different shape.

Why does this happen? It's often just a matter of timing, says Dr. Hoang. "Your child might have one breast that starts growing before the other," she says.

Usually, asymmetrical breasts will even out as puberty progresses, says Dr. Hoang. But many people have some degree of breast asymmetry even once breasts are fully developed, and that's completely normal.

Are Stretch Marks Normal?

Stretch marks (called striae) are common during times of rapid growth as the skin is overstretched. It's quite common for teens to get stretch marks on their breasts during puberty, says Dr. Hoang. "Newer marks will look pink, red, or purple in color," she describes. "As your child ages, the color of their stretch marks will lighten in color, but may not completely disappear."

When Do People Start Wearing Bras?

Wearing a bra is a personal decision, and you can help your child by being supportive and giving them options. All teens are different, but many feel like they need extra support soon after breast development. They may also feel self-conscious in clothing if they're not wearing a bra.

During the early stages of breast development, your child might only need a training bra, says Dr. Hoang. They can move to a more supportive bra as their breast development continues, she adds.

Other Normal Variations of Breast Development

Most children and parents don't notice any abnormalities during breast development, but sometimes variations occur. Many of these variations are harmless, such as polythelia, which is characterized by extra (supernumerary) nipples. Other normal variations include having tubular shaped breasts or bilaterally smaller breasts, says Dr. Hoang.

Teens who have abnormally large breasts, especially as compared to the rest of their body, may have a condition called macromastia. "Teens with large breasts may feel discomfort that can be relieved with a supportive bra," says Dr. Hoang. "Other teens may feel breast pain with exercise or with their menstrual cycle."

In rare cases, breast reduction surgery may be helpful, but the American Academy of Pediatrics (AAP) doesn't recommend considering this until two or three years after menstruation has begun and physical growth is completed.

When To See a Health Care Provider

There's a wide variation of "normal" when it comes to breast development and appearance. That said, some concerning symptoms should be brought up with your child's health care provider.

One of these symptoms is unusual masses or lumps on your child's breast, says Dr. Brooks. Most conditions that cause breast masses or lumps during the teenage years are benign, including fibroadenomas (non-cancerous tumors) and fibrocystic breasts (characterized by lumpy fibrous tissue). Still, "all concerning or new lumps should be evaluated because there are some very rare conditions in teens that are not benign," notes Dr. Brooks.

You should also consult your health care provider if your child is late to develop breasts or show signs of puberty. "If there is no breast development at all by age 13, no menses by age 16, or no menses occurring within three years after the onset of [breast development], it's considered to be pubertal delay," Dr. Brooks. If this happens to your child, further evaluation may be necessary.

Other symptoms that could use professional evaluation include nipple discharge, extreme breast swelling or tenderness, redness or discoloration, and anything else that's concerning. Keep in mind that it never hurts to reach out to your pediatrician about any changes that happen during the teen years. "Any time a patient or parent is concerned about their development, it's OK to ask us about it!" assures Dr. Brooks. "Body development is never anything to be embarrassed about."