Teen Breast Development Guide: What's Normal & What to Expect

Puberty is a time of massive change, and for many girls, breast development is one of the first and most noticeable signs. It can be exciting, but it can also bring a lot of questions and even some anxiety. “Is this normal?” “Why do they hurt?” “When will they stop growing?”

This guide is designed for both teenagers navigating these changes and parents looking to support them. We’ll break down the science of how breasts grow, what the “Tanner Stages” are, and address common concerns like asymmetry and pain.

#When Does Breast Development Start?

Breast development (medically known as thelarche) usually begins between the ages of 8 and 13. However, every body is unique. Some girls may start as early as 7, while others might not see changes until 14 or 15.

[!NOTE] > Genetics plays a huge role. If your mother developed early or late, there’s a good chance you might follow a similar pattern.

#The 5 Stages of Breast Growth (Tanner Stages)

Doctors use a scale called the Tanner Stages to track physical development during puberty.

#Stage 1: Pre-Puberty

There is no visible breast tissue yet. The chest is flat, and only the nipple is raised.

#Stage 2: The Breast Bud (Ages 8-13)

This is the first sign of puberty. A small, firm mound of tissue (the “bud”) forms under the nipple. The areola (the dark skin around the nipple) may get larger. It’s very common for one side to start before the other!

#Stage 3: Tissue Growth (Ages 12-14)

The breast tissue grows larger and extends beyond the areola. The breast starts to take on a more defined shape. This is often when girls start wearing their first training bra.

#Stage 4: Secondary Mound (Ages 13-15)

The areola and nipple form a secondary mound that rises above the rest of the breast tissue. Not every girl experiences this distinct stage, and that’s perfectly normal.

#Stage 5: Adult Stage (Ages 15+)

The breast reaches its full adult size and shape. The secondary mound from Stage 4 smooths out into the general contour of the breast.

#Common Questions & Concerns

#“My breasts hurt. Is something wrong?”

Breast buds can be tender! It is completely normal for developing breasts to feel sore, itchy, or sensitive. This is growing pains for your chest. As you get older, you might notice tenderness right before your period—this is due to hormonal changes.

#“One is bigger than the other!”

Asymmetry is the rule, not the exception. Especially in the early stages (like for a 15-year-old), it is incredibly common for one breast to grow faster than the other. For most women, they even out over time, but having slight differences in size is normal for adult women too.

#“I feel a lump behind my nipple.”

In boys and girls going through puberty, a small, firm, button-sized lump directly under the nipple is usually just the developing breast bud. However, if you find a lump away from the nipple or in the armpit, it’s a good idea to get it checked.

#When to See a Doctor

While most changes are normal, you should see a specialist if:

• You have redness, heat, or severe pain in the breast.
• There is discharge (fluid) coming from the nipple.
• You notice a distinct lump that isn’t the general breast bud.
• You haven’t started any breast development by age 14.

#Tips for Parents

• Start the conversation early. Don’t wait for her to ask. Mention that body changes are normal.
• Go bra shopping together. Make it a positive experience. Start with comfortable crop tops or sports bras before moving to wired bras.
• Normalize asymmetry. Reassure her that lopsidedness is temporary and very common.

#Conclusion

Whether you’re 12, 15, or older, remember that your body is on its own timeline. There is no “perfect” size or shape. Taking care of your health, wearing a supportive bra, and being kind to your body are the most important things you can do.

[!TIP] > Next Step: Learn how to find the perfect support in our Complete Bra Size & Fitting Guide.

Return to the main guide: Breast Care Tips