This is a congenital defect where the back of the nasal passage is blocked, usually by abnormal bony or membranous tissue.
Choanal atresia may be unilateral or bilateral.
Sometimes, a unilateral choanal atresia is not detected until much later in life because the baby manages to get along with only one patent nostril.
If both nostrils are affected, this is a very serious condition because the baby will then be unable to breathe right after birth as babies are obligate nasal breathers. These babies usually require resuscitation right after birth. The only suitable treatment is surgery.