What causes a baby to be born deaf but look normal?

What? There is absolutely no reason why a deaf child should look any different than a non deaf child.
Wrong question. A better way to ask this is why it is hard to realize that they are deaf.A common viral infection that a mother can have during pregnancy can attack the fetal ear nerve and cause deafness.Since it may have no other effect on the baby, they can be born deaf and it not be realized until later.Most states now have newborn screening programs for every baby to try to identify these kids early.