Q: What is congenital diaphragmatic hernia?
The diaphragm is a thin sheet of muscle that separates the chest from the abdomen. In the growing embryo the diaphragm is completely formed by 10 weeks gestation.
Approximately 1 in 4000 fetuses have an inborn defect where the diaphragm is incompletely formed. The opening in the diaphragm may allow bowel, stomach or even the liver to enter the chest. This is called congenital diaphragmatic hernia. After birth the hole in the diaphragm can be closed without difficulty. However, in fetal life the abdominal contents that enter the chest leave insufficient space for the lungs to develop normally.
When the lungs have insufficient space several parts of the lung that are essential do not develop normally. The little air sac, or alveoli that allow the air to enter the lung are decreased in numbers. The distance between the air entering the lung and the blood vessels that take up the oxygen is increased. The number of blood vessels available to transport oxygen back to the heart are decreased. This type of underdevelopment of the lungs is called pulmonary hypoplasia.
The fetus does not need to use the lungs because the placenta provides oxygen and nutrients. If pulmonary hypoplasia is severe the lungs may not be able to function properly. Under these circumstances the babies breathing may need external support. This can be provided by mechanical ventilation.
Many forms of mechanical ventilation are available to support the baby after birth. However, if the pulmonary hypoplasia is too severe the lungs may never be able to provide enough oxygen for the baby to survive. This is called lethal pulmonary hypoplasia.
One of the major complications of congenital diaphragmatic hernia is the risk for lethal pulmonary hypoplasia.
Q: What are the chances that my baby will survive?
The survival chances depend entirely on the development of the lungs prior to birth. Earlier and more severe compression of the lung tissue results in greater developmental impairment. Therefore survival can be predicted before birth by examining the lung size.
The relative lung size can be assessed by two-dimensional ultrasound, three-dimensional ultrasound, or fetal magnetic resonance imaging (MRI). The ratio of lung and the fetal head circumference (lung-to-head ratio) is an effective method to predict the survival in congenital diaphragmatic hernia.
When the lung-to-head ratio is below 1 the diaphragmatic hernia is considered severe because survival is lowest in these babies.
Q: How is FETO performed?
This minimally invasive fetoscopic procedure is performed under epidural or local anaesthesia.
Prior to FETO, medication will be given to your fetus for pain relief and also to prevent fetal movements.
After the fetus is gently moved into the best position a small 3 mm skin incision is made.
The fetoscope is introduced through the skin into the uterus and guided into the mouth and trachea of your fetus.
When the fetoscope has been directed into the trachea a small catheter is used to guide the balloon to its proper placement site.
Once this is achieved the balloon is inflated with fluid and left in the trachea.
The balloon remains in the trachea of the fetus until 32-34 weeks gestation. During this time your fetus will be monitored with ultrasound.
Since the placenta provides the oxygen for the fetus the balloon does not interfere with fetal breathing. Prior to birth however the balloon must be removed in order for the baby to be able to breathe after birth.
The balloon can be removed in several ways. While pregnant a second fetoscopy may be performed. Alternatively the balloon may be punctured under ultrasound guidance using a needle. Once the balloon is removed you can deliver normally.
If the baby is born before the balloon is removed puncture can be performed after/at birth using a needle or by direct visualization of the balloon (tracheoscopy).
Because of the special expertise needed, delivery in a tertiary care center with experience in the care of babies with diaphragmatic hernia is important.
Q: What are the risks for me?
Because of the minimally invasive nature of the procedure the risks for the mother is small. These include bleeding and infection.
Q: What are the risks for my baby?
The principal risk for the baby is preterm delivery. This may follow premature rupture of membranes or preterm labor that has been triggered by the small hole made into the uterus. The balloon itself has not been shown to have any adverse effects.
Q: What are the chances my baby will survive after the intervention?
In fetuses that are eligible for FETO due to their severity of the diaphragmatic hernia the survival is typically 10 percent without any treatment. The FETO treatment increases this survival rate to approximately 50 percent Additional factors such as the gestational age at delivery also affect survival. These factors will be discussed with you in detail during your consultation with us.
Q: What are the alternatives?
You may choose to have no intervention. If this is your choice the fetus will need to be monitored and delivery will need to be at a tertiary level hospital experienced in the care of babies with diaphragmatic hernia.
Q: What happens after my baby is born?
After birth your baby will be admitted to the neonatal intensive care unit. Here, your baby may need help with breathing on a ventilator. Typically a small tube will be placed in the stomach to prevent the baby to swallow air. The surgical repair of the hernia will be performed once the baby has been stabilized. During these initial days, the main indicator how your baby will do is the ability of the lungs to absorb oxygen, release carbon dioxide and have a normal blood pressure. All of these questions will be reviewed in detail during our multidisciplinary consultation.