CDH is a birth defect characterized by the development, very early in gestation, of a hole in the diaphragm, the breathing muscle that separates the chest from the abdomen. As a result, the intestines and other organs in the abdomen can move into the chest and press on the developing lungs. This prevents the lungs from growing and developing normally. In severe cases, CDH can lead to serious disease and death at birth. For these babies, treatment before birth may allow the lungs to grow enough before birth so these children are capable of surviving and thriving.