Trisomy is a type of condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities. It is a type of aneuploidy and can arise with any chromosome, but frequently result in miscarriage, rather than live birth.
The autosomal trisomy is classified into different types that survive to give birth in human beings are:

  • Trisomy 21(Down Syndrome)
  • Trisomy 18(Edwards Syndrome)
  • Trisomy 13(Patau Syndrome)
  • Trisomy 9
  • Trisomy 8(Warkany Syndrome)
  • Trisomy 22

Signs of Trisomy disorders during pregnancy:

In rare cases, signs of trisomy disorders may be visible during the pregnancy. Some of these signs may include:

  • Too much amniotic fluid around the baby (polyhydramnios)
  • Baby only has one artery in umbilical cord
  • A smaller than expected placenta
  • The baby is small for its gestational date
  • The baby is less active than expected
  • Congenital defects, containing cleft palate or heart abnormalities, are gathered for the period of ultrasound scans.


Prenatal tests are used to detect trisomy disorders. These include:

  • Ultrasound scans: Sound waves are used to create a picture
  • Maternal serum screening: A specialized blood test
  • Amniocentesis: A sample of the amniotic fluid is taken and examined
  • Chorionic villi sampling: A sample of cells from the chorion, the tissue that will finally become the placenta, is taken and observed.
  • Non-invasive prenatal testing (NIPT): A different type of screening test that measures fetal DNA circulating in the mother’s blood.

Where to get help for Trisomy:

  • Paediatrician or Doctor
  • Victorian Clinical Genetics Services.
    Royal Children's Hospital Flemington Rd Parkville,
    Victoria, 3052 Australia.
    Tel. (03) 8341 6201
  • SOFT. Australia – Support Organisation for Trisomy in Australia
    198 Oak Road,
    Kirrawee NSW 2232, Australia
    Tel. (02) 9521 6039

Things to remember:

  • Humans have 23 pairs of chromosomes.
  • A trisomy is a chromosomal disorder illustrated by an additional chromosome, so the person has 47 instead of 46.
  • Down syndrome, Edward syndrome and Patau syndrome are common types of trisomy.