Tracheo-oesophageal fistula and oesophageal atresia. read about them but still not sure of causes?

Congenital: Tracheo-esophageal fistula means that the two tubes are connected by a small hole. It is present at birth and the first evidence of its presence is when the first feed is given for the infant chokes as the food enters the trachea from the esophagus. Esopageal atresia is a (usually) partial failure of the esophagus to develop.

Unknown: Cause of esophageal atresia and tracheo-esophageal atresia is unknown.