Was Born with an Extra Chromosome?

What is Down Syndrome? Down syndrome is a condition in which a person has an extra chromosome. Chromosomes are small “packages” of genes in the body. They determine how a baby's body forms and functions as it grows during pregnancy and after birth.

What does it mean to be born with an extra chromosome?

A "trisomy" means that the baby has an extra chromosome in some or all of the body's cells. In the case of trisomy 18, the baby has three copies of chromosome 18. This causes many of the baby's organs to develop in an abnormal way.

What happens if a human has an extra chromosome?

For example, an extra copy of chromosome 21 causes Down syndrome (trisomy 21). Chromosomal abnormalities can also cause miscarriage, disease, or problems in growth or development. The most common type of chromosomal abnormality is known as aneuploidy, an abnormal chromosome number due to an extra or missing chromosome.