<prompt> Answer this question truthfullyWhat is tracheoesophageal fistula and what causes it?  <response>: <reason> Tracheoesophageal fistula TEF is a medical condition that is present at birth and results in an abnormal connection between the esophagus and trachea. This condition is caused by a failure of the esophagus and trachea to separate during fetal development. TEF can cause problems with feeding and breathing and requires surgical intervention to correct. 