What is Congenital Diaphragmatic Hernia (CDH)?
CDH is a fetal abnormality that occurs very early in pregnancy (10-12 weeks), when the baby’s diaphragm does not form properly. An opening in the diaphragm leads to contents of the abdomen—such as the stomach, small intestine, spleen, liver, or kidney—developing in the chest cavity instead of the abdomen. The hernia usually occurs on the left side, but can also occur in the right side. The displaced organs prevent the lungs from developing properly.
CDH is rare, occurring in 1 out of 2,500 to 3,000 births. It varies in severity from very severe, causing immediate distress, to mild, causing no neonatal effect at all. CDH is not related to anything the mother did or did not do during pregnancy.
Once diagnosed, how is the severity of CDH assessed?
At 22 to 28 weeks of gestation, the St. Louis Fetal Care Institute team performs a focused ultrasound, a fetal MRI, and a fetal echocardiogram (ECHO) to assess the severity of the CDH. We also offer genetic testing to determine if a chromosomal abnormality has caused the CDH.
The team uses several measurements to understand how the CDH will affect the baby. We measure the lung-to-head ratio, the liver position, the total lung volume, the response of the fetal lungs to oxygen, and we look for any abnormalities suggestive of a genetic cause. This is a critical assessment.
What happens at delivery and beyond?
Most babies with less severe CDH can be delivered by whatever route the mother desires, usually vaginally. The baby is quickly evaluated by the neonatologists (pediatrician specialized in newborn care) and usually a breathing tube is inserted so that a breathing machine can help the baby breathe.
The care after birth is quite complex, but generally the baby is stabilized from a breathing and heart function standpoint. Once these issues are stable and working well, the surgery to repair the hole in the diaphragm can be performed. After this, the baby must learn to breathe and eat without assistance. This can take several weeks. The neonatologists and pediatric surgeons work very closely with the baby’s family to navigate through the hospitalization.
In severe cases of CDH, we recommend a special delivery procedure. The delivery is by an “EXIT” procedure, in which the mother has a cesarean section delivery while asleep under general anesthesia. During this operation, the fetal surgeons have time to evaluate the airway. A breathing tube is inserted and breathing is assisted using a ventilator machine.
Once we are confident that the lungs are working well, the baby is fully delivered by cutting the umbilical cord. The care after this is essentially the same as with any other baby with CDH.
What is ECMO?
In some cases, the CDH is so severe that the lungs and heart cannot provide the necessary functions to survive. Because a CDH baby’s lungs are so small, they cannot transition from the environment in the womb to that in air so quickly. More development time is needed for the lungs to function optimally. If this is the case ECMO is used.
ECMO is short for extracorporeal membrane oxygenation. It is a machine which functions just like the lungs, exchanging gasses like oxygen. The neonatologists and pediatric surgeons watch your baby very carefully to determine if ECMO is needed. If so, then surgery is needed to place tubes in the baby’s blood vessels, so that blood can be removed, run through the ECMO machine, and returned to the baby.
What is tracheal occlusion fetal surgery and how does it work?
While developing in the uterus, the fetus’ lungs constantly make fluid, which escapes through the fetus’ mouth and empties into the amniotic fluid. When a baby has CDH the lungs are crowded out by other organs, making it hard for the lungs to develop normally. Tracheal occlusion blocks the trachea so that the fluid in the lungs cannot escape. The fluid builds up, expanding the lungs, allowing them to grow faster than normal. If successful, tracheal occlusion makes the lungs bigger so the child can breathe better and get adequate oxygen once he or she is born.
During the procedure, the fetal surgeon makes a tiny incision in the mother and the mother’s uterus to perform tracheal occlusion. Traditionally, a tiny detachable balloon is placed in the trachea, which works well to obstruct the airway. This method presents a number of challenges, the biggest of which is that the balloon must be removed for the baby to breathe at birth. In more than half of the cases, mothers have presented in labor after balloon placement, and the balloon had to be removed urgently.
The St. Louis Fetal Care Institute is conducting research on a new way to address this problem, a Hydrogel tracheal occlusion. This innovative procedure involved the surgeon injecting a polymer gel, known as Hydrogel, into the fetus’s trachea. This substance blocked the trachea and resulted in increased lung growth. The gel was reabsorbed by the baby during pregnancy. When the baby was born, the airway was clear and unobstructed. The purpose of this research trial is to determine how long the gel caused tracheal occlusion during pregnancy. This procedure is currently not being performed because study results are being evaluated and analyzed.