About trisomy 13

Trisomy 13, or Patau syndrome, is a chromosomal disorder. It happens when a baby’s cells have three copies of chromosome 13, rather than the usual two.

Most unborn babies with trisomy 13 are miscarried or stillborn.

Babies who survive pregnancy usually die in the first month of life. About 10% live beyond one year.

Babies born with trisomy 13, or Patau syndrome, often have:

  • low birth weight
  • brain and heart problems
  • eye defects
  • abnormal hands and feet
  • difficulties with feeding and breathing.

Children with trisomy 13 who survive beyond infancy have severe intellectual disability.

Some children might have only a few features of trisomy 13, and other children might have many.

The way children are affected by trisomy 13 depends on whether all of their cells contain three copies of chromosome 13, or only some of their cells. When only some of a child’s cells have an extra copy of chromosome 13, this is called ‘mosaic’ Patau syndrome. Children with mosaic Patau syndrome have a milder form of the condition.

For normal human development, we need 46 chromosomes (23 pairs carrying genetic material from each parent) in all of the cells in our bodies. Chromosomal abnormalities are when there are missing or extra chromosomes or changes in the structure or arrangement of the chromosomes.

Diagnosis of trisomy 13

You can have tests during pregnancy to help you find out whether your baby has trisomy 13.

Screening tests give you information about how likely it is that your baby has trisomy 13, but these tests don’t give you a definite answer. Examples of screening tests include:

  • non-invasive prenatal testing (NIPT): you give a small amount of blood, which is tested for parts of your baby’s DNA
  • first trimester combined screening test: this combines a blood test from you with a measurement from your 12-week ultrasound scan.

Depending on the results of screening tests, you might want to have diagnostic testing. Diagnostic testing can tell you definitely whether your baby has trisomy 13.

Diagnostic tests include chorionic villus sampling (CVS) and amniocentesis. Both of these tests are very accurate, but they also have some risks.

You can talk to your doctor or midwife to get more information about these tests.

Trisomy 13 can also be diagnosed at birth because there are key physical features that your doctor can see. If the doctor thinks your baby has trisomy 13, the doctor will confirm this by giving your baby a blood test.

Being told that your unborn or new baby has trisomy 13 can be a big shock for you and your family. Talking with other parents can be a great way to get support. You can connect with other parents in similar situations by joining a face-to-face or online support group.

Support and treatment for children with trisomy 13 and their families

You might have some difficult decisions to make about your pregnancy if your unborn baby gets a diagnosis of trisomy 13. Your midwife, GP, obstetrician or a genetic counsellor will be able to give you information and support to help you decide what’s best for your family.

For babies born with trisomy 13, doctors and parents often have to make difficult decisions about treatment. Many parents need to make a very difficult choice between making their baby comfortable and prolonging life through invasive surgery.

The following professionals might also be able to help you before and after your child is born:

The National Disability Insurance Scheme (NDIS) might support your child with trisomy 13, as well as you and your family. Our guide has answers to your questions about the NDIS.

Causes of trisomy 13

Trisomy 13, or Patau syndrome, is most often caused by a random error in the formation of a parent’s eggs or sperm.

Less often, this error happens after conception, while the baby is still developing in the womb.

The older a mother is when she gets pregnant, the higher the chance she has of having a baby with Patau syndrome.

If you have one baby with Patau syndrome, the chance of having another baby with the syndrome is usually very low. But this depends on the type of condition your child has. Genetic testing can give you more information about this.