Malformation of the diaphragm allows the abdominal organs to push into the chest cavity, hindering proper lung formation.

[citation needed] This rare anterior defect of the diaphragm is variably referred to as a Morgagni, retrosternal, or parasternal hernia.

Accounting for approximately 2% of all CDH cases, it is characterized by herniation through the foramina of Morgagni which are located immediately adjacent and posterior to the xiphoid process of the sternum.

[4] The diagnosis of congenital diaphragmatic eventration is used when there is abnormal displacement (i.e. elevation) of part or all of an otherwise intact diaphragm into the chest cavity.

This rare type of CDH occurs because in the region of eventration the diaphragm is thinner, allowing the abdominal viscera to protrude upwards.

[citation needed] There are genetic causes of CDH[5] including aneuploidies, chromosome copy number variants, and single gene mutations.

Individual rates vary greatly dependent upon multiple factors: size of hernia, organs involved, additional birth defects and/or genetic problems, amount of lung growth, age and size at birth, type of treatments, timing of treatments, complications (such as infections) and lack of lung function.