Without medical intervention, the expected outcomes for fetuses diagnosed with CHAOS can be divided into thirds.
One third of the fetuses will develop progressive nonimmune hydrops and die in utero.
One third of the fetuses will have spontaneous perforation through the tracheal or laryngeal atresia, or less commonly, experience decompression through a fistula (abnormal passageway) in the area of the trachea and esophagus (the tube that branches off the trachea and carries food to the stomach).
One third will have stable hydrops, tolerating it reasonably well until 30 to 32 weeks of gestation, when preterm labor or fetal distress will likely develop. At that point, an EXIT procedure can be performed.
A fetus diagnosed in the third trimester with CHAOS but without associated anomalies or hydrops likely has incomplete airway obstruction and will do well until delivery by the EXIT procedure. Laryngoscopy, bronchoscopy and tracheostomy will be required immediately before delivery, so the fetus needs to be managed by the EXIT procedure to secure the airway while being maintained on placental support.
There is little information regarding the long-term outcome for children affected with CHAOS. In cases of simple laryngeal cyst or web, normal laryngeal function can be anticipated. The outcome in cases of more significant laryngeal malformation is less certain regarding voice and the ability to have the tracheostomy closed. Because infants with CHAOS have not survived until recently, our information on long-term outcome is limited.