Trisomy 18

Trisomy 18, the second most common autosomal chromosomal disorder after trisomy 21, is characteristic with the presence of an extra chromosome 18; either full, mosaic trisomy, or partial trisomy 18q. The clinical pattern is characterised by growth deficiency that starts in the prenatal period; specific craniofacial features and marked psychomotor and cognitive developmental delay. Typical craniofacial features include dolichocephaly, short palpebral fissures, micrognathia, external anomalies of the ears, and redundant skin at the back of the neck. The presence of major systemic malformations is common, and any organ and system can be affected. Cardiovascular, respiratory, ophthalmologic, musculoskeletal, genitourinary, neoplastic, neurologic, and developmental problems can occur. Prenatal and early postnatal infant mortality rates are high. The postnatal median survival of children is 3 to 4.5 days; approximately 50% of babies with trisomy 18 live longer than one week and only five to 10% of children survive beyond the first year. Central apnoea, cardiac failure due to cardiac malformations, respiratory insufficiency due to hypoventilation, aspiration, and/or upper airway obstruction are major causes of death. Due to the short life expectancy, there are ethical concerns regarding offering interventional surgical operation to the children with Edwards syndrome.