An apparently healthy newborn with a hardy appetite has begun feedings with for- mula. When she is laid down in the crib after feeding, she experiences projectile vomiting. Which of the following conditions is a prob- able cause of this vomiting?

B. An esophageal hiatal hernia is a herniation of the stomach through the esophageal hia-tus into the pleural cavity. This compromises the esophagogastric sphincter so that stomach contents can easily reflux into the esophagus. The combination of a full stomach after feeding and lying down in the crib will cause vomiting in this newborn.