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Genetic and Rare Diseases Information Center (GARD)

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Trisomy 13


Other Names for this Disease
  • Chromosome 13, trisomy 13 complete
  • Complete trisomy 13 syndrome
  • D trisomy syndrome (formerly)
  • Patau syndrome
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Your Question

I previously had a pregnancy affected by trisomy 13. What is the chance of this happening again in a future pregnancy?  Should my partner and I get checked for anything in particular?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What causes trisomy 13?

Most cases of trisomy 13 are not inherited and are caused by random events during the formation of eggs and sperm in healthy parents (prior to conception). The condition typically results from having three copies of chromosome 13 in each cell in the body, instead of the usual two copies. This is referred to as complete, or full, trisomy 13. The extra genetic material disrupts the normal course of development, causing the characteristic features of trisomy 13.

Trisomy 13 can also occur when part of chromosome 13 becomes attached (translocated) to another chromosome during the formation of reproductive cells (eggs and sperm) or very early in fetal development. This is referred to as translocation trisomy 13. Individuals with this type have two normal copies of chromosome 13, plus an extra copy of chromosome 13 attached to another chromosome.

In rare cases, only part of chromosome 13 is present in three copies in each cell; this is called partial trisomy 13.  In other rare cases, a person has an extra copy of chromosome 13 in only some of the body's cells; this is called mosaic trisomy 13. The severity of mosaic trisomy 13 depends on the type and number of cells that have the extra chromosome.[1]
Last updated: 1/20/2015

If a previous pregnancy was affected by trisomy 13, what is the chance of having another pregnancy affected with this condition?

Because trisomy 13 is very rare and most often occurs by chance, it is very unlikely that a woman would have more than one pregnancy affected by this condition, though it is difficult to determine what the exact chance is.[2]  The risk of having a second pregnancy affected varies depending on whether the initial trisomy 13 occurred because an extra chromosome 13 was attached to another chromosome (translocation) in one of the parents or because two copies of chromosome 13 didn't separate during the making of an egg or sperm (nondisjunction). 

One study estimated that there is a 3 in 1000 chance for women who have had a pregnancy affected by trisomy 13 to have a second pregnancy affected by trisomy 13; there is also approximately a 9 in 1000 chance for a future pregnancy to be affected by trisomy of another chromosome, such as trisomy 21 or trisomy 18.[2]  Due to these risks, a woman who has had a pregnancy affected by trisomy 13 should discuss this diagnosis with her personal physicians and should be followed closely during any future pregnancies.[3]
Last updated: 4/16/2012

What testing might be available for someone who had a previous pregnancy affected by trisomy 13?

Most trisomy 13 pregnancies occur by chance.  However, in rare instances, a parent may have an increased chance of having a pregnancy affected by this condition because they have a translocation that involves chromosome 13.  Each parent can have a blood test called a karyotype to look at the chromosomes and determine if there is a translocation.

Prenatal testing (such as maternal blood screeningfetal ultrasoundchorionic villus sampling, or amniocentesis) is available to determine if a current pregnancy is at risk for or is affected by trisomy 13 or other chromosome disorders.  It is important to discuss the benefits, risks, and limitations of these options with one's personal physicians before having these tests.
Last updated: 4/16/2012

How can I find a genetics professional in my area?

Genetics clinics are a source of information for individuals and families regarding genetic conditions, treatment, inheritance, and genetic risks to other family members. More information about genetic consultations is available from Genetics Home Reference. To find a genetics clinic, we recommend that you contact your primary healthcare provider for a referral.

The following online resources can help you find a genetics professional in your community:

Last updated: 6/22/2012

References
Other Names for this Disease
  • Chromosome 13, trisomy 13 complete
  • Complete trisomy 13 syndrome
  • D trisomy syndrome (formerly)
  • Patau syndrome
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.