Also called Edwards syndrome. Represents chromosomal variations due to an extra chromosome 18 (complete, mosaic, or partial) occurring in 1 in 5500 live births. Characterized by multiple severe intrauterine growth abnormalities, low birth weight, and a greatly increased risk of stillbirth and neonatal mortality. Other signs and symptoms include characteristic craniofacial features (micrognathia, microcephaly, prominent occiput), short sternum, overlapping fingers with clenched fists, hypoplastic fingernails, rocker-bottom feet, intellectual disability, malformed kidneys, heart defects, and other organ malformations. Risk factors include increased maternal age. Parental genetic counseling may be warranted.

Management of neonates is complex, requiring a high degree of vigilance and numerous interventions such as tube feeding, gastrostomy, and airway clearance. Most infants die in the first year of life with <10% living beyond the first decade. Common causes of neonatal and infant death are progressive pulmonary hypertension and cardiac or cardiopulmonary arrest.