Which of the following is NOT one of the three most common tracheo-esophageal malformations?

The correct choice identifies pyloric stenosis as the condition that does not belong to the category of tracheo-esophageal malformations. Pyloric stenosis is a gastrointestinal condition affecting the pylorus, the opening from the stomach into the small intestine, leading to projectile vomiting and dehydration in infants. It does not involve any malformations of the trachea or esophagus.

Esophageal atresia refers to a congenital condition where the esophagus does not form properly, resulting in a discontinuity. Tracheo-esophageal fistula is a malformation where there is an abnormal connection between the trachea and the esophagus, which can lead to serious complications, especially during feeding. The condition that combines both, known as tracheo-esophageal fistula with esophageal atresia, incorporates elements of both of these malformations, illustrating how they are interconnected.

In summary, recognizing that pyloric stenosis affects a different part of the gastrointestinal tract than the trachea and esophagus underscores why it is not classified among the three common tracheo-esophageal malformations.