Occur on 0.1-0.2% of live births.
Occur in 1 in 160 live births.
Extra copies of chromosomes 13, 18, and 21 account for the majority of chromosomal abnormalities not related to sex chromosomes at birth.
About 1% of newborns possess a gross chromosomal abnormality and nearly 5% of patients under the age of 25 years develop a serious disease with a significant genetic component.
Advancing maternal age has a adverse effect on the incidence of chromosomal abnormalities.
Advanced paternal age associated with increased risk of autosomal dominant diseases including achondroplasia and Marfan’s syndrome.
Trisomy 21, Down syndrome, seen in about 1 in 800 births.
Trisomy 18 seen in 1 of 6000 children.
Trisomy 13 seen in 1 of 10,000 children.