The diaphragm is a thin layer of muscle that separates the chest and abdominal cavity. It plays an important role in breathing. A congenital (at or before birth) diaphragmatic hernia (CDH) occurs when the diaphragm does not form properly during pregnancy. Typically, this results in a small hole in the diaphragm, or in rare cases it does not form at all. The opening allows for the organs in the abdomen (stomach, liver, intestines) to push or herniate into the chest, which can prevent the normal growth and development of the lungs. 1,600 babies are born with CDH every year in the U.S occurs or about 1 in 2,000 – 1 in 5,000 live births.

Most cases of diaphragmatic hernia are believed to be multi-factorial in origin. Multi-factorial means that many factors, both genetic and environmental, are involved. It is thought that multiple genes from both parents, as well as a number of environmental factors that scientists do not yet fully understand, contribute to the development of a diaphragmatic hernia.

We know that genetic changes play a significant role in most cases of CDH, however, there is still much to be learned about this relationship. One of the most common genetic causes of CDH are structural changes to the chromosomes.
If your genetic information was a library, then the chromosomes are like the books. We each have 23 pairs of ‘books’ and we receive one copy from mom and one copy from dad. On these ‘books’ are the words or genes that spell out the instructions and blueprints that tell our body how to grow and develop.
Sometimes, there are structural changes to the chromosomes; pieces of a ‘book’ are either duplicated or missing altogether. These situations may explain about 10-35% of CDH cases. We can detect these changes with either a karyotype which takes a picture of these chromosomes or a microarray which measures the amount of each chromosome and can detect smaller changes to the chromosomes.
Another genetic cause of CDH are changes or misspellings in the genes or instructions themselves. We know some of these misspellings that cause CDH but we do not know them all. Some of these changes cause known diseases and children can be at risk for other symptoms or defects, but other genetic changes are only linked to CDH.
Some cases of CDH are inherited from the parents and therefore other family members or future children may be at risk for developing CDH. However, it is important to understand that ‘genetic’ is not necessarily the same thing as ‘inherited.’ While each parent does pass on half of their DNA to their children, a small portion of each child’s genetic instructions will be completely new in them. This is one reason why children aren’t an exact blend of their parents. In these cases, there may be no family history and the risk for future children is negligible.

All pregnancies have a 2-3% risk for some type of birth defect. One type of birth defect is a CDH.
Parents who have had one child with an isolated CDH, meaning no problems other than the CDH, are at increased risk to have another child with the same problem. For most families this chance is approximately 1-2% or 1 in 100 to 2 in 100.
If there is a known cause for the CDH, the recurrence risk depends on the specific diagnosis.

Many babies with CDH are identified before birth by ultrasounds performed during pregnancy. The ultrasound provides pictures of the baby’s organs and allows the doctors to see whether the abdominal organs are in the right position. The ultrasound also allows doctors to check the position of the heart and lungs of the developing baby. In some cases, the CDH is not diagnosed until after the baby is born. Because of their underdeveloped lungs, babies with CDH will have difficulty breathing right after birth. As a result, a chest x-ray is done to evaluate the lungs. The chest x-ray in infants with CDH allows the doctors and nurses to see that parts of the stomach, intestine, and/or liver are in the chest area.