CDH, or congenital diaphragmatic hernia, is a birth defect where a baby is born with a hole in the diaphragm, the large muscle that separates the chest from the abdomen. This opening allows abdominal organs like the stomach, intestines, liver, or spleen to shift upward into the chest cavity during development. When those organs crowd the chest, the lungs don’t have enough room to grow properly, which creates serious breathing problems at birth. CDH affects roughly 1 to 3 out of every 10,000 babies born in the United States.
How CDH Affects a Baby’s Development
The diaphragm normally forms during the first trimester. When it doesn’t close completely, a gap remains. As the baby grows in the womb, abdominal organs gradually push through that gap and into the chest. The real danger isn’t the displaced organs themselves but what they do to the lungs. With organs taking up space in the chest cavity, one or both lungs can’t expand and develop normally. This is called pulmonary hypoplasia, and it means the lungs are smaller and less mature than they should be at birth.
The underdeveloped lungs also tend to have abnormal blood vessels, which leads to a condition called pulmonary hypertension, where blood pressure in the lungs is dangerously high. Together, small lungs and high lung pressure make it difficult for a newborn to get enough oxygen on their own. Most babies with CDH need breathing support immediately after delivery.
Types of Diaphragmatic Hernia
There are two main types, and they differ by where the hole forms in the diaphragm.
Bochdalek hernia is by far the most common, accounting for 80 to 90 percent of all cases. The opening is typically on the left side of the diaphragm. Because of its location, the stomach, spleen, intestines, and sometimes the liver can all migrate into the chest.
Morgagni hernia is much rarer, making up only about 2 percent of cases. The opening forms in the middle or right side of the diaphragm, and it usually involves the liver or intestines moving upward. Morgagni hernias tend to be less severe and are sometimes not diagnosed until later in infancy or even childhood.
How CDH Is Diagnosed Before Birth
Most cases of CDH are detected on a routine prenatal ultrasound, often during the mid-pregnancy anatomy scan around 18 to 22 weeks. The ultrasound may show organs in an unexpected position, fluid around the lungs, or a heart that’s been pushed to one side of the chest.
Once CDH is identified, doctors use several markers to estimate how severe it is. One of the most important is the lung-to-head ratio (LHR), a measurement taken between 20 and 29 weeks that compares the size of the baby’s visible lung tissue to the size of the head. A low LHR, particularly below 1.0, signals significant lung underdevelopment and is associated with a more difficult course after birth. Whether the liver has also shifted into the chest and how far the stomach has moved from its normal position are additional indicators of severity.
What Happens After Birth
Babies with CDH are typically delivered at a hospital with a specialized neonatal intensive care unit (NICU) so a full team is ready. Because these babies often can’t breathe effectively on their own, they are placed on a ventilator shortly after delivery. Some need a more advanced form of life support called ECMO, which takes over the work of the lungs and heart by pumping and oxygenating the baby’s blood outside the body. The most common reasons a baby needs ECMO are severe pulmonary hypertension, heart failure, or the need for breathing support so aggressive it could damage the lungs further.
The goal in the first hours and days is stabilization, not surgery. Doctors wait until the baby’s breathing and circulation are steady before attempting a repair. Some centers prefer to wait until pulmonary hypertension fully resolves, though this can take weeks or even months and carries its own risks, including infection. In practice, many surgical teams will move forward once the baby is stable, even if some degree of pulmonary hypertension remains.
Surgical Repair
Surgery is the only way to fix CDH. The surgeon moves the displaced organs back down into the abdomen and closes the hole in the diaphragm. When the hole is small enough, it can be stitched closed directly. Larger defects require a patch, a piece of synthetic material or tissue that bridges the gap. Patch repairs are associated with a higher chance of certain long-term complications, but for many babies, the defect is simply too large to close without one.
After surgery, the baby remains in the NICU. Recovery depends heavily on how underdeveloped the lungs are and whether complications like pulmonary hypertension persist. Some babies spend weeks in the hospital; others with more severe cases may stay for months. The lungs continue to grow after surgery, but how much they catch up varies from baby to baby.
A Procedure Done Before Birth
For the most severe cases, an experimental procedure called FETO (fetoscopic endoluminal tracheal occlusion) may be offered while the baby is still in the womb. A tiny balloon is placed inside the baby’s airway using a small camera. The balloon traps fluid in the developing lungs, and the pressure from that fluid encourages lung growth over several weeks. The balloon is then deflated and removed before delivery.
FETO is only considered when lung development is critically low, generally when the observed lung size is 30 percent or less of what’s expected for a left-sided hernia, or 45 percent or less for a right-sided one. It’s performed between 27 and 29 weeks of gestation and is not an option for pregnancies with twins, additional birth defects, or certain maternal health conditions. Only a handful of specialized fetal surgery centers offer it.
Long-Term Health for CDH Survivors
Surviving CDH is a significant milestone, but many children face ongoing health challenges that require regular follow-up. The most common issues fall into a few categories.
Lung and Breathing Problems
Even after repair, the lungs may remain smaller or function differently than normal. Pulmonary hypertension persists after hospital discharge in an estimated 8 to 38 percent of survivors, though most cases resolve over time. A smaller subset of children have persistent pulmonary hypertension that requires continued monitoring and treatment. Some children are also more susceptible to respiratory infections or develop chronic lung disease, especially those who needed prolonged ventilation or ECMO as newborns.
Reflux and Feeding Difficulties
Gastroesophageal reflux (GERD) is extremely common in CDH survivors, affecting anywhere from 30 to 80 percent. The displaced organs and surgical repair can change the anatomy around the junction between the esophagus and stomach, making reflux more likely. Some children have “silent” reflux that causes esophageal irritation without obvious symptoms, so routine screening is important even when a child seems comfortable.
Developmental Delays
Neurodevelopmental challenges affect a notable number of CDH survivors across multiple areas: motor skills (both fine and gross), language, cognition, and visual-spatial abilities. Children who required ECMO as newborns tend to have higher rates of difficulty with verbal memory, working memory, and processing speed. CDH survivors as a group also show increased rates of learning disabilities, attention deficit hyperactivity disorder, and sensorineural hearing loss, which is reported in 7 to 56 percent depending on the study. Early intervention services and regular developmental assessments help identify and address these issues as early as possible.
What Causes CDH
In most cases, the exact cause is unknown. The diaphragm forms early in pregnancy, and CDH happens when that process is disrupted. It can occur as an isolated defect or alongside other birth defects. Some cases are linked to chromosomal abnormalities or genetic syndromes, which is why genetic testing is often recommended after diagnosis. However, many babies with CDH have no identifiable genetic cause, and there is usually nothing a parent did or could have done to prevent it.