Congenital High Airway Obstruction Syndrome

Congenital high airway obstruction syndrome, or CHAOS, is a blockage of the fetus's trachea (windpipe) or larynx (voice box). This obstruction can be due to a number of factors, including narrowing of the airway, called stenosis; a web-like membrane; or even an area of the trachea that is missing, called atresia.

During pregnancy, the fetal lungs constantly produce fluid. If the airway is blocked, this fluid can't escape out the mouth and the baby's lungs become distended. This can put pressure on the heart and affect its function. If the heart can't beat effectively, congestive heart failure can occur.

The cause of CHAOS is currently unknown. It is a very rare condition and is not thought to recur in families.

The outcome for CHAOS depends greatly on what's causing the obstruction. If the obstruction is minor — a thin tissue membrane covering the larynx — it may be correctable with minor surgery before or after birth with no lasting complications.

A complete blockage of the larynx or a missing section of trachea is more serious. In these cases, the baby will not be able to breathe when born, and will need a tracheostomy after birth as well as multiple operations to correct the airway. There may also be problems with the ability to talk and to eat and drink by mouth. In more extreme cases, in which the lung swelling endangers the heart function, the fetus may need surgery before birth.

The condition can also be complicated by the presence of other birth defects, so it is important to test for other abnormalities. Amniocentesis can be used to test for problems with the baby's chromosomes, and an echocardiogram can be used to look more closely at the fetal heart structure and function.

If the chromosomes are normal and there are no additional birth defects other than CHAOS, the severity of the condition depends on the type of malformation causing the airway obstruction.

To determine the severity of the problem, a number of tests are recommended:

  • Amniocentesis to look for chromosomal abnormalities
  • A level II ultrasound to look for other abnormalities and to examine the anatomy of the airway
  • A fetal echocardiogram to determine if the fetus has an associated heart defect or if the function of the heart has been affected
  • An MRI to obtain an accurate picture of the airway and determine the level and length of the obstruction in the airway

After CHAOS is fully diagnosed through a formal evaluation, your doctor will explain your treatment options. In severe cases where the fetus has hydrops, fetal surgery to relieve the obstruction may be offered. Hydrops is the build-up of excess fluid, which can be seen in the fetal abdomen, lungs, skin or scalp.

If there is no fetal hydrops, we recommend delivering the baby via the EXIT (Ex Utero Intrapartum Treatment) procedure. The EXIT procedure is for babies who are known to have an airway obstruction. The goal is to provide the baby with a functioning airway so that oxygen can be delivered to the lungs after the baby is separated from placenta.

EXIT procedure

The EXIT procedure is a planned, specialized delivery. It should only be performed at a hospital that can provide a team consisting of a pediatric surgeon, an obstetrician, an anesthesiologist and a neonatologist.

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