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Genetic and Rare Diseases Information Center (GARD)

Other Names for this Disease
  • Chromosome 13, trisomy 13 complete
  • Complete trisomy 13 syndrome
  • D trisomy syndrome (formerly)
  • Patau syndrome
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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?

Almost all cases of trisomy 13 are caused by random events during the formation of an egg or sperm in healthy parents.  Most often, the error occurs during cell division when a pair of chromosomes 13 stick together in one cell instead of separating into two cells (this is called nondisjunction); this produces an egg or sperm cell (reproductive cells) with an extra copy of chromosome 13.  If one of these reproductive cells with an extra copy of chromosome 13 contributes to the genetic makeup of a child, the child will have an extra chromosome 13 in each cell of the body and have trisomy 13.

Translocation trisomy 13 occurs when a child inherits an extra chromosome 13 that is attached to another chromosome.  A parent with normal chromosomes can have a rearrangement of genetic material between chromosome 13 and another chromosome such that the two chromosome become attached to each other. These rearrangements are called balanced translocations because there is no extra material from chromosome 13. A person with a balanced translocation involving chromosome 13 has an increased chance of having a child with trisomy 13, because they may pass on the chromosome that is abnormally attached to chromosome 13, resulting in the child having extra chromosome material.[1]
Last updated: 4/16/2012

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