An abnormal connection in one or more places between the esophagus and the trachea. Normally, these are two separate tubes, one leading to the stomach and the other to the lungs. TEF results from a failure of normal development in utero. The affected baby cannot swallow his own saliva and mucus. When the baby tries to eat, food may enter the lungs, causing the baby to choke, cough and sometimes turn blue. Tracheo-esophageal fistula is usually discovered soon after birth. Babies (slightly more males than females) are born with this condition in about 1 out of every 3000 to 5000 births.