Causes. Micromastia can be congenital or acquired disorder and may be unilateral or bilateral. Congenital causes include ulnar–mammary syndrome (caused by mutations in the TBX3 gene), Poland syndrome, Turner syndrome, and congenital adrenal hyperplasia.

What does it mean if you are flat chested?

If you describe a woman as flat-chested, you mean that she has small breasts. [disapproval]

Is being flat chested genetic?

Genetics doesn't play a role in breast size

Although genetics aren't the end-all, be-all when it comes to breast size, they do play some role. ... In addition, as people gain weight, their breasts also become larger." Luciani explained that sagging, breast volume, and breast shape can also be genetically-influenced.