Does anything bad happen if you get breast implants under the age of 18?

Possibly: Yes. It is possible to alter or affect breast growth. A mature breast size may not yet have been achieved and further growth may occur. Possible damage to nerves or the breast ducts may also occur although this can occur at any age.

Depends: The answer to your question depends on what you are defining as “bad". Generally speaking, best for young ladies to wait until their breasts have “matured” prior to undergoing elective breast surgery. There are exceptions where patients with significant congenital anomalies and/or asymmetry may benefit from breast surgery earlier in life. Best wishes.