Edwards syndrome is a rare genetic disorder in fetuses, caused by an extra copy of chromosome 18 in the genome. When children have this syndrome, they often have developmental delays and may have other serious birth defects.

In fetuses with choroid plexus cysts, 2.1% have a numerical chromosomal abnormality, and the majority of fetuses will have other abnormalities that can be seen on ultrasound. However, when no other abnormalities are seen on ultrasound, the risk of a numerical chromosomal abnormality is approximately 1 in 300.