Congenital Diaphragm Hernia
A congenital diaphragm hernia (CDH) is a birth defect in which an abnormal opening occurs in the diaphragm during fetal development, allowing contents of the abdomen (stomach) to migrate into the chest. CHD is rare and occurs in approximately 1 out of every 2,500 live births.
About Congenital Diaphragm Hernia
The diaphragm is a large muscle that separates the abdomen (stomach) from the chest. At around 9 to 10 weeks of gestation, the folds in tissue that form the diaphragm may not closely completely, leaving an opening in the muscle. This leads to a defect in the diaphragm known as a congenital diaphragm hernia (CDH). The opening in the fetal diaphragm allows the stomach, small intestine, large intestine, and other large organs, such as the liver and spleen, to protrude into the chest. This causes the lung that is located on the same side of the hernia to become compressed, which prevents its growth (pulmonary hypoplasia). The extra organs in the chest can also shift the heart over to the side of the chest opposite of the hernia, which can affect the growth of the other fetal lung. A CDH can range from a small defect to a complete lack of the diaphragm.
Initially CDHs are categorized as one of the following:
- Left-sided CDHs make up 85% of cases
- Right-sided CDHs make up 10-15% of cases
- Bilateral (present on both sides) make up the remaining 5% or fewer cases
CDHs can be described as “liver up” or “liver down,” depending on whether the liver has moved into the chest of the fetus. “Liver up” hernias seem to cause more breathing difficulties for babies after they are born. On occasion, a CDH can appear and then disappear on subsequent prenatal ultrasounds; these cases are known as transient or sliding hernias. An eventration of the diaphragm is a mild form of a hernia that occurs when the diaphragm is not completely formed with all of the typical types of tissues. In these cases, the abdominal organs are still located in the abdomen but appear to be located in the lower chest due to a ballooning of the diaphragm. These newborns rarely experience breathing difficulties at birth.
Symptoms of Congenital Diaphragm Hernia
In rare cases, ultrasounds during pregnancy will not detect the CHD. However, once the baby is born, doctors may diagnose the condition if they notice the baby has difficulty breathing. A chest X-ray can show whether organs normally in the abdomen have moved into the chest, the lungs appear smaller in size, or the lungs have shifted to one side.
Causes of Congenital Diaphragm Hernia
The cause of a CHD remains unknown; however, certain chromosomal problems found in fetuses can sometimes present with a CDH.
Complications Associated With Congenital Diaphragm Hernia
CDHs are rarely associated with any health risks for the pregnant mother. Approximately 40% of CDH cases are associated with other problems in the fetus, and the other 60% of cases are isolated events. In 20% of CDH cases, a heart anomaly occurs. In 10-35% of CDH cases, chromosome problems occur. Because the placenta is providing oxygen to the fetus in the womb, a fetus with a CDH usually does not suffer any consequences of its anomaly prior to birth. Some fetuses with a CDH may develop problems with a slowing of their growth known as intrauterine growth restriction.
Major complications associated with a CDH in a newborn can include poor development of the lungs (pulmonary hypoplasia) and high blood pressure inside the fetal lungs (pulmonary hypertension). This causes a strain on the heart and difficulty with blood normal blood flow into the lungs to acquire oxygen. Both pulmonary hypoplasia and pulmonary hypertension contribute to significant breathing problems for the newborn soon after birth.
After birth, babies that survive their initial stay in the hospital required for their CDH diagnosis may need oxygen support for a prolonged period of time due to poor lung development (bronchopulmonary dysplasia). Babies that require an operation to patch and repair their CDH are also at higher risk for developing a recurrent hernia that requires a second operation later in life. Some babies with a CHD may experience a delay in meeting their developmental milestones. Higher incidences of scoliosis (curvature of the spine) have been reported in the development of these children. Some babies may have long-term feeding problems and require a gastrostomy tube, which is special tube that is placed into the belly to allow nutrition to be provided directly into the stomach.
Diagnosing Congenital Diaphragm Hernia
CDHs are commonly found at the time of an anatomy ultrasound at around 20 weeks (5 months) of gestation. Only 50-80% of cases are diagnosed on ultrasound during pregnancy. The ultrasound of a baby with a CHD will indicate the fetal stomach has moved into the chest next to the heart and the heart shifted over to the side of the chest opposite of the hernia.
To assess the severity of the CHD and to check for other potential fetal anomalies, you will undergo a complete assessment of the fetal anatomy by an experienced physician using ultrasound. Fetal magnetic resonance imaging (MRI) can also be useful in these cases. This type of study works like a CT scan but does not involve X-rays. Instead, a special magnet is used to see structures in the fetus that cannot be seen easily with ultrasound. An MRI is safe for both the fetus and pregnant mother. Finally, you will be offered a chromosomal assessment through chorion villus biopsy (biopsy of the placenta) or amniocentesis (fluid taken from around the fetus with a needle placed under ultrasound guidance). Analysis of the fetal DNA should involve a karyotype (counting the number of chromosomes) as well as a microarray (special method of looking for very small changes in the chromosomes).
Using ultrasound, your doctors can predict the outcome of your baby with a CHD by taking a measurement known as a lung-to-head ratio (LHR). The size of the lung on the side opposite to the CDH is measured and the number is compared to the development of other fetuses at the same point in pregnancy (observed-to-expected ratio or O/E). An O/E LHR of less than 25% indicates a severe CDH with a high likelihood for significant breathing problems after birth and a decreased chance for survival. An O/E LHR between 25-45% indicates a moderate case of the CHD. An O/E LHR greater than 45% indicates the likelihood of a milder form of the CDH.
Ultrasound can also detect whether the fetal liver has herniated into the fetal chest; however, the edges of the liver in the fetal chest can often be difficult to distinguish on ultrasound. Therefore, an MRI can be useful to determine how much of the fetal liver has herniated. A liver hernia value of more than 21% indicates a more severe case of the CDH. Ultrasound can also be used to categorize the location of the stomach in the chest. As more of the liver herniates into the fetal chest, the stomach is pushed further back in the fetus. The position is graded between 1 and 4. A higher number indicates more of the liver is in the chest, resulting in a poorer prognosis. MRI can also be used to measure the total volume of the fetal lungs. An O/E lung volume of less than 32% is associated with a poor prognosis.
Pregnancy With Congenital Diaphragm Hernia
Occasionally, the kinking of the fetal stomach in the chest can cause the fetus to experience difficulty swallowing. This can result in excess fluid in the sac surrounding the fetus (polyhydramnios), which can lead to maternal discomfort and, in some cases, problems with maternal breathing. In these cases, the fluid can be temporarily drained from the sac around the fetus through a procedure known as amnioreduction. During this procedure, a needle is placed into the uterus using ultrasound for guidance. The needle is then connected to a tube and the excess fluid is drained over a 20- to 30-minute period of time.
After the initial ultrasound evaluation, you will likely be scheduled for a fetal echocardiogram (specialized ultrasound of the heart) to assess the fetal heart and fetal magnetic resonance imaging (MRI) to assess the other organ systems in the fetus. You will be scheduled to meet with a genetic counselor to discuss the consideration of chorionic villus sampling or amniocentesis to evaluate the chromosomes of the fetus. During your pregnancy, you may also be scheduled to meet with a pediatric surgeon depending on whether the defect will be fixed with surgery.
You will be scheduled for ultrasounds every 3 to 4 weeks to monitor your baby’s rate of growth. The growth of the lung on the opposite side of the CDH will also be monitored by measuring the LHR.
Typically, most women with a baby in utero with an CDH will be induced at around 39 weeks (1 weeks before your due date) of gestation. A vaginal delivery is safe for fetuses with a CDH.
Treating Congenital Diaphragm Hernia
There are currently no forms of fetal surgery available for treating a CDH. Currently, several studies are being conducted to determine whether placing a small balloon in the windpipe of the fetus can help the lungs to grow larger in size (fetoscopic tracheal occlusion or FETO). The balloon would be placed using a small telescope (fetoscope) that is inserted into the uterus at around 26 weeks of gestation (6 and half months). The balloon remains in place for approximately 6 weeks before being removed in a second procedure. Initial results of these studies have been encouraging, but the procedure should be considered experimental at this point in time.
Evaluation After Birth
After birth, your baby will likely require a breathing tube be placed in their windpipe to provide oxygen (endotracheal intubation). This will be performed by a neonatologist in the delivery room. Your baby will then be transported to the neonatal intensive care unit (NICU).
Depending on the extent of breathing difficulties your baby is experiencing, the following treatments may be used in a progressive fashion:
- Conventional ventilation: This involves endotracheal intubation with a standard ventilator (breathing machine).
- High frequency oscillatory ventilation (HFOV): This involves endotracheal intubation with an oscillator ventilator, which delivers tiny puffs of oxygen at a rate of 800 to 900 breaths each minute.
- Nitrous oxide: This involves a special gas that is added to the oxygen to help relax the muscles in the blood vessels in the baby’s lungs if pulmonary hypertension is present.
- Sildenafil: This involves a form of medication that is sometimes used to treat pulmonary hypertension.
- Extracorporeal membrane oxygenation (ECMO): This is used when the baby’s oxygen levels are still poor despite the interventions outlined above. A series of tubes are placed in the baby’s blood vessels in the neck and connected to a machine that provides oxygen directly into the baby’s bloodstream.
Once your baby is stable in the NICU, your pediatric surgeons will perform surgery to repair the CDH. In some cases, if the defect in the diaphragm is large in size, a patch may be used to repair the defect. The surgery for CDH typically takes place between 4 and 10 days after birth.
Care Team Approach
The Comprehensive Fetal Care Center, a clinical partnership between Dell Children's Medical Center and UT Health Austin, takes a multidisciplinary approach to your child’s care. This means you and your child will benefit from the expertise of multiple specialists across a variety of disciplines. Your care team will include fetal medicine specialists, obstetricians, neonatologists, sonographers, palliative care providers, fetal center advanced practice providers, fetal center nurse coordinators, genetic counselors, and more, who work together to provide unparalleled care for patients every step of the way. We collaborate with our colleagues at The University of Texas at Austin and the Dell Medical School to utilize the latest research, diagnostic, and treatment techniques, allowing us to identify new therapies to improve treatment outcomes. We are committed to communicating and coordinating your care with your other healthcare providers to ensure that we are providing you with comprehensive, whole-person care.