This rare anomaly usually results from laryngeal or tracheal atresia. The normal egress of lung fluid is obstructed, and the tracheobronchial tree and lungs become massively distended. Sonographically, the lungs appear brightly echogenic, the bronchi are dilated, the diaphragm is flattened or everted, and the heart is compressed (Fig. 10-26). Venous return is impaired and ascites develops, typically followed by hydrops. In one review of 118 cases, associated anomalies were identiied in more than 50 percent (Sanford, 2012). Congenital high airway obstruction sequence (CHAOS) is a feature of the autosomal recessive Fraser syndrome and has been associated with the 22q 11.2 deletion syndrome. In some cases, the obstructed airway spontaneously perforates, which potentially confers a better prognosis. he EIT procedure has significantly improved outcome in selected cases (Chap. 16, p. 327).
FIGURE 10-25 Pulmonary sequestration. A. This transverse image at the level of the 4-chamber view of the heart depicts a pulmonary sequestration involving the left lower lobe in a 25-week fetus. Mass effect leads to dextroposition of the heart to the right side of the chest.
B. A sagittal image shows the pulmonary sequestration supplied by a branch of the abdominal aorta. C. Over the next 3 weeks, a large ipsilateral pleural effusion develops (asterisk), resulting in mediastinal shift and dextroposition of the heart to the far right thorax. D. Following placement of a double-pigtail shunt through the chest wall and into the effusion, the effusion drained and the lung significantly reexpanded. Arrows points to coils of the pigtail shunt. (Used with permission from Dr. Elaine Duryea.)
FIGURE 10-26 Congenital high airway obstruction sequence (CHAOS). The lungs appear brightly echogenic, and one is marked by an "L." The bronchi, one of which is noted by an arrow, are dilated with fluid. Flattening and eversion of the diaphragm is common, as is ascites (asterisks).
Cardiac malformations are the most common class of congenital anomalies, and their overall prevalence is 8 in 1000 births (Cragan, 2009). Almost 90 percent of cardiac defects are multifactorial or polygenic in origin, another 1 to 2 percent result from a single-gene disorder or gene-deletion syndrome, and 1 to 2 percent stem from exposure to a teratogen such as isotretinoin, hydantoin, or maternal diabetes. Based on data from population-based registries, approximately 1 in 8 liveborn and stillborn neonates with a congenital heart defect has a chromosomal abnormality (Dolk, 2010; Hartman, 201l). Of chromosomal abnormalities associated with cardiac anomalies, trisomy 21 accounts for more than 50 percent of cases. Others are trisomy 18, 22q 11.2 deletion, trisomy 13, and monosomy X (Hartman, 2011). Of these aneuploid fetuses, 50 to 70 percent also have extracardiac anomalies. Chromo defects are found.
Traditionally, detection of congenital cardiac anomalies is more challenging than for anomalies of other organ systems.