GeneCare Medical Genetics Center - Physician Information on Amniocentesis Postnatal Chromosome Analysis Postnatal chromosome analysis is performed on peripheral blood, products of conception or skin biopsy specimens from individuals suspected of having a chromosome abnormality.
Chromosomes are units of genetic information.
Individuals with a chromosome abnormality usually have mild to severe mental retardation and birth defects. The most common chromosome abnormality is an extra 21 chromosome resulting in Down syndrome. Chromosome abnormalities are caused at conception when an abnormal sperm or egg from one parent fuses with a normal sperm or egg from the other parent. The abnormal sperm or egg contains extra or missing chromosomal material. These abnormal sperm or eggs are present in everyone, but the risk of an abnormal conception does increase significantly with the parents' ages.