Trisomy 13

Trisomy 13 

If you have just found out through prenatal testing that your baby has Trisomy 13 or may have Trisomy 13 and are looking for more information, the Genetic Support Foundation is a good starting point.

There are other important resources out there, including your doctor and genetic counselor. We have also compiled a list of resources that can provide you with additional information and support.

After reviewing the information below, if you have a question that you are having difficulty finding an answer for, please feel free to contact us.


Overview of important information about Trisomy 13

Trisomy 13, also called Patau syndrome, is a chromosomal condition that occurs in approximately 1 in 10,000 live-born babies (it is more common than this, but most babies with Trisomy 13 miscarry during the pregnancy). Trisomy 13 is the result of the baby having 3 copies of chromosome 13 instead of the typical two copies.  This extra chromosome causes the intellectual disability and physical problems associated with Trisomy 13.  Most babies who are born with this condition pass away shortly after birth or within the first year of life, however, some can live longer.  The chance of Trisomy 13 does increase  as mom’s age increases.  There is nothing mom or dad can do to cause or prevent Trisomy 13.

Most cases of Trisomy 13 involve the individual having an extra copy of chromosome 13 in all of the cells of their body, which is called full Trisomy 13 and is definitely the most common type of Trisomy 13.  However, there are a couple of other types of Trisomy 13:

  • Translocation Trisomy 13- This type of Trisomy 13 occurs when mom or dad carry what is called a balanced translocation involving chromosome 13.  They are healthy and well but there is an increased chance with each pregnancy for the baby to have translocation Trisomy 13, which is 3 copies of chromosome 13, just in a different arrangement. The characteristics of translocation Trisomy 13 are the same as full Trisomy 13.
  • Mosaic Trisomy 13– In this situation, only some of the cells (not all) in the body have an extra chromosome 13. mosaic Trisomy 13 may be less severe than full Trisomy 13.
  • Partial Trisomy 13– This can occur if mom or dad carries a rearrangement of their chromosomes that involves chromosome 13. In this situation, the baby may have extra genetic information from part of chromosome 13 but not all of chromosome 13 as seen in full Trisomy 13.

Both mosaic Trisomy 13 and partial Trisomy 13 may be mild or severe, depending on how many and which cells have the extra 13 in mosaic trisomy 13 and how much of the chromosome 13 is in extra in partial Trisomy 13.

What causes Trisomy 13?

As humans, we typically have 23 pairs of chromosomes in each of our cells or a total of 46 chromosomes. Individuals with Patau Syndrome or Trisomy 13 have an extra copy of the material from chromosome #13. In most cases, this is due to a whole extra copy of chromosome #13, which is called Trisomy 13. This increases in incidence as mom ages. However, there are other ways that an individual can get an extra copy of the material from chromosome 13, namely, translocation trisomy 13 and mosaic Trisomy 13. Regardless of what type, this extra genetic material from chromosome 13 is the reason that individuals with this condition typically have severe intellectual disability and an increased risk for other birth defects and health concerns.

Trisomy 13 cannot be cured. Most cases of Trisomy 13 are sporadic, meaning it does not run in families. With sporadic Trisomy 13, it is unlikely that if you have one child with it that future children would also have it, although the likelihood of this increases slightly above your age related chance. There are some cases of Trisomy 13 that can run in the family (when caused by a translocation), but it is rare for this to happen. In the type that runs in the family, recurrence risk or chance of future children having Trisomy 13 is higher. A picture of the baby’s chromosomes (karyotype) can determine if it is the type that is sporadic  or the type that runs in the family.

Is there anything I can do to cause or prevent Trisomy 13?

Based on current research, there is nothing that mom or dad can do to cause or prevent Trisomy 13.  This is a condition that does increase in risk as mom’s age increases, however, women of all ages can have a baby with Trisomy 13.

What are some common things seen on ultrasound in babies with Trisomy 13?

There are many characteristics seen more frequently in babies with Trisomy 13 on ultrasound during the pregnancy.  For example, babies with Trisomy 13 are more likely to have heart defects, brain abnormalities, extra fingers and other findings.  These things can also be seen in babies without Trisomy 13, so for definitive information regarding Trisomy 13 during the pregnancy, amniocentesis or CVS is recommended.

What is the long term outcome for individuals with Trisomy 13?

Due to the fact that Trisomy 13 is associated with severe mental and physical abnormalities, many babies with Trisomy 13 die before birth or within the first month of life. Typically up to 10% of children with Trisomy 13 live past their first year.

Individuals with mosaic Trisomy 13 (meaning only some of their cells have an extra chromosome 13) may have a less severe long term outcome than those with full Trisomy 13.  It is difficult to predict outcome prior to seeing how the baby develops over time.

Individuals with partial Trisomy 13 (part of their chromosome 13 is in extra but not the whole chromosome) may have a long term outcome much different and possibly less severe than full Trisomy 13 as well.

How does having a baby with Trisomy 13 affect a family?

There is not a lot of data to answer this question, however, this is an excerpt pulled from a study done in 2012 titled, The Experience of Families with Children with Trisomy 13 and 18 in Social Networks1.

“Although most parents described their children as having significant neurodevelopmental disabilities, almost all parents reported a positive view of family life and the quality of life of their child with trisomy 13 or trisomy 18. These parents overwhelmingly described surviving children as happy and stated that they were able to communicate with them to understand their needs. Parents seemed to accept their children’s limitations and to celebrate their small achievements. When children died, parents viewed their short lives as being valuable. Yet at the same time, parents acknowledged that there were significant financial sacrifices and that their children experienced more pain than other children. Most parents reported that their family was strengthened since the birth, and often the death, of a child with trisomy 13 or trisomy 18.”1

What are my options if Trisomy 13 is diagnosed during pregnancy?

Please see our section on receiving a prenatal diagnosis for more information about your options.  This is a difficult time and you are not alone.  If there is anything we can do to help you, please contact us.

Other Resources


1. Janvier, A, Farlow B, Wilfond, BS. 2012. The Experience of Families with Children with Trisomy 13 and 18 in Social Networks. Pediatrics 130(2):293-8.


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