Trisomy 21 is the most common trisomy at the time of birth. Also called Down syndrome, it is associated with moderate to severe intellectual disabilities and may also lead to digestive disease, congenital heart defects and other malformations.
Trisomy 18 and 13 are associated with a high rate of miscarriage. These babies are born with severe brain abnormalities and often have congenital heart defects as well as other birth defects. Most affected individuals die before or soon after birth, and very few survive beyond the first year of life.
The sex chromosomes (X and Y) determine whether we are male or female. X and Y chromosome conditions occur when there is a missing, extra, or incomplete copy of one of the sex chromosomes. The Harmony with X, Y test can assess risk for XXX, XYY, XXYY, XXY (Klinefelter syndrome), and a missing X chromosome in a girl (Turner syndrome). There is significant variability in the severity of these conditions, but most individuals have mild, if any, physical or behavioural features. If the mother is interested in having this optional testing, she should talk with her healthcare provider to determine if it is right for her.