As a girl gets closer to puberty, the first signs of breast development start to show. This happens when the ovaries begin making a hormone called estrogen.
- Fat starts to build up under the skin, making the breasts begin to grow.
- The milk ducts inside the breasts also begin to grow.
- Around the same time, pubic hair and underarm hair may also start to appear.
Once a girl starts having periods (menstruation), the breasts continue to develop:
- Glands that make milk begin to form at the ends of the milk ducts.
- More glands and small structures, called lobules, continue to grow inside the breasts.
Everyone develops at a different pace. Some girls may grow faster or slower than others and that’s totally normal.
Doctors describe breast growth in five stages, from the beginning to full development:
Stage 1 (Preadolescent)
- The chest is flat.
- Only the tip of the nipple is raised.
Stage 2 (Breast Bud Stage)
- Small bumps called “buds” form under the nipple.
- The breast and nipple start to rise a little.
- The dark area around the nipple (called the areola) gets bigger.
Stage 3
- The breasts grow larger.
- Gland tissues (the part that makes milk later) begins to form.
Stage 4
- The nipple and areola stick out more and form a second small bump on top of the breast.
Stage 5 (Adult Stage)
- The breasts are fully grown and rounded.
- Only the nipple sticks out.