The diaphragm is a muscle that separates the abdomen from the chest. The pressure in the abdomen is greater than the pressure in the chest. When the diaphragm does not form or does not form properly, leaving a gap, the pressure in the abdomen pushes the stomach, bowel and other organs into the chest.
In congenital diaphragmatic hernia (CDH), the defect in the diaphragm allows abdominal organs to occupy the fetal chest, which does not allow the lungs to develop properly. This is called pulmonary hypoplasia, or lack of lung development. In addition, the arteries within the lungs become thickened, increasing the blood pressure within the lungs, a condition called pulmonary hypertension.
Approximately 80% of CDH’s are on the left side (left-sided), 15% are right-sided and 5% are on both sides (bilateral). At birth, approximately 50% of babies may die either from pulmonary hypoplasia, pulmonary hypertension or both. Babies that survive may have long-term breathing problems, pulmonary hypertension and other complications, such as brain bleeds, gastrointestinal problems (for example, reflux) and others.
Treatment of CDH before birth (antenatal) has been tried in several different ways to try to avoid death or long-term complications after birth. The first attempts were done by repairing the hernia while the baby was still in the womb, using open fetal surgery.That approach was abandoned, both from significant maternal complications as well as from lack of improved outcomes over expectant management.
A second approach involved blocking the airway of the fetus. Researchers discovered that blocking the airway of the fetus would result in accumulation of lung fluid beneath the blockage, which expanded the lungs and resulted in lung development as well. This technique is called tracheal occlusion, or TO.
Quintero and collaborators showed that it is possible to enter the airway of the fetus without having to open the maternal abdomen or the uterus (percutaneous approach) to block the fetal airway with a special device. Because the blockage is done from within the airway, it was called “intraluminal”, as opposed to blockage from outside the airway (for example, by tying off the airway). If lung development is achieved, the tracheal occlusion device is removed at the time of birth and the baby undergoes correction of the hernia after birth.
Currently, several centers worldwide are offering intraluminal fetal TO for the antenatal treatment of CDH. Most centers are using a detachable balloon and are reporting approximately 36% survival in severe CDH cases (the ones that otherwise theoretically would have died). Our center offers a different technique involving the placement of a covered stent, which meets all of the requirements for the surgery. Using such technique, our current survival rates are approximately 85%.
How can one predict which fetuses will do well without antenatal treatment and which would not, and therefore would potentially benefit from tracheal occlusion?
If the compression of the fetal lungs is not severe, such that the lung size is preserved, those babies are likely to do well and do not need antenatal surgery. To gauge if the size of the lungs is small, which would justify antenatal treatment, researchers have proposed different ultrasound formulas:
Our group specializes in the assessment, counseling and management of patients with high-risk pregnancies in Florida.