If you wear a bra that's either a little bit big or a little too small, will it cause your chest to not grow? – Gilly*
No. A girl's bra won't affect the growth of her breasts. That's because genes and hormones control breast growth, not what a girl wears.
Bras don't make breasts grow or stop growing, but wearing the right-size bra may help you feel more comfortable. Bras that are too small may cause breast pain because of how sensitive some girls' breasts can be as they grow. And bras that are too big won't offer enough support, which could also lead to discomfort if your breasts move or bounce around too much. Find a bra that's the right size for you and comfortable to wear.
Want your breasts to develop the way nature intended? Eat a variety of healthy foods and exercise regularly. And don't worry if you don't develop at the same rate as your friends. Some girls develop earlier, others later. A girl's breasts can keep growing and changing into her late teens.