Congenital
high airway obstruction syndrome (CHAOS) is defined as complete or partial
obstruction of the fetal upper airways. This clinical condition was brought
into notice firstly by Hedrick in the late 1900s. CHAOS
is usually caused by atresia or stenosis of the larynx or trachea. If the
syndrome is unrecognized during the prenatal period, it usually results in
stillbirth or death shortly after delivery.
Fortunately, more cases can be recognized in utero nowadays, as there are
significant technical improvements in prenatal imaging. Bilaterally enlarged
hyperechoic lungs, dilated airways, and flattened or inverted diaphragm are the
typical prenatal sonographic findings. Fetal ascites and nonimmune hydrops may
also be associated with the clinical condition. Due to the recently described
management options, prenatal definition of fetal airway obstruction has come
into prominence with the hope of neonatal outcome improvements. We
present a similar case in a 29 year old woman with 21 weeks gestational age.
Case: A 29-year-old woman with a previous two live birth was referred for a routine second trimester antenatal ultrasound at 21weeks gestational age. Ultrasound examination revealed that the fetus had bilateral large echogenic lungs. The principal bronchi appeared dilated (Figure 1). No cystic lesions were seen in the lungs. The diaphragm was inverted. The heart was centrally placed and seemed to be compressed by the enlarged lungs, and there was moderate ascites. However, amniotic fluid was normal. The intra-cranial fetal structures, cerebellum, upper lip, spine, both kidneys, stomach bubble, urinary bladder, and the limbs were normal. The placenta was normal appearing. The femur length and bi-parietal diameter corresponded to 20 weeks of gestation while the abdominal circumference was corresponding to 25 weeks due to the presence of ascites.
Based on ultrasound findings, the diagnosis of CHAOS due to laryngeal atresia was made.
The parents were counselled regarding the relatively poor prognosis of the syndrome, however, they wanted to continue the pregnancy.
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