What causes Edwards syndrome?

Edwards syndrome is caused by the presence of an extra 18th chromosome, a genetic condition known as trisomy 18. This abnormality leads to various developmental and physical challenges that can severely affect an individual's health and longevity. The majority of individuals with Edwards syndrome display a range of symptoms, including severe intellectual disability, distinctive physical features, and congenital heart defects.

The condition arises during the formation of reproductive cells and can occur due to improper cell division, resulting in an embryo with three copies of chromosome 18 instead of the usual two. This genetic anomaly can have profound developmental implications, and while some individuals may survive into childhood, many do not survive past their first year.

In contrast, other options refer to different chromosomal conditions. Trisomy 21 refers to Down syndrome, 45 chromosomes suggests a missing chromosome (typically associated with Turner syndrome), and monosomy 13 relates to Patau syndrome, which involves a different set of genetic complications. Each of these conditions has distinct characteristics and implications that differentiate them from Edwards syndrome.