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Patau Syndrome (Trisomy 13)


Updated April 17, 2014

Chromosomal abnormalities are one of the most common causes of miscarriage and stillbirth. In a condition known as trisomy, an affected individual has three copies of a particular chromosome instead of two (human beings are supposed to have 23 pairs of chromosomes). Different trisomies have different effects on an individual's health, with some being barely noticeable and others leading to poor longterm prognoses.

Trisomy 13, known as Patau Syndrome, falls toward the more severe end of the spectrum.


Somewhere between 1 in 10,000 and 1 in 21,700 babies is born with Patau Syndrome. The incidence during pregnancy is higher, however -- researchers believe that about 95% of babies with Patau Syndrome are miscarried or stillborn. No one knows why some survive to term while others do not. Many babies who do survive to term die within their first month. Only 5% to 10% of babies with Patau Syndrome survive to their first birthday.


Prenatal screening tests such as the alphafetoprotein test and pregnancy ultrasound can reveal markers of possible chromosomal conditions but cannot provide a diagnosis. Only genetic tests such as amniocentesis and CVS (or blood tests after the baby's birth) can provide a solid diagnosis of Patau Syndrome. It's also possible that Patau Syndrome can be revealed as the cause of a pregnancy loss if the couple seeks genetic karyotyping on the baby after a miscarriage or stillbirth.

Prognosis for Liveborn Babies:

Babies who are born with Patau Syndrome will likely have characteristic physical abnormalities and problems with their internal organs. The majority of affected babies die in the first month after birth or within the first year due to the health complications associated with the condition. There are some reports of individuals with Patau Syndrome surviving to adulthood but always with developmental disorders of varying severity.

Types of Patau Syndrome:

As with other trisomy disorders, there are three possible types of Patau Syndrome: full trisomy 13, partial trisomy 13, and mosaic trisomy 13. The most common is full trisomy 13 in which there are three full copies of chromosome 13. The latter two types are more rare. In partial trisomy 13, there would be two full copies of chromosome 13 and an additional extra part of chromosome 13, and mosaic trisomy 13 would mean that some of the body's cells had three copies of chromosome 13 whereas others had the normal two copies.

Risk of Recurrence:

Most of the time, the cause of trisomy 13 is a random error in cell division during the formation of the egg or sperm, meaning the problem is already present at the time of fertilization -– and the disorder will not recur. In more rare cases, the parent may have a balanced translocation involving chromosome 13 and will have increased risk of having a baby affected by the problem again (this applies to partial trisomy 13).

Deciding What to Do If Your Baby Has Patau Syndrome:

One of the first questions you may be asked if your baby receives a diagnosis of Patau Syndrome is whether you want to continue the pregnancy (or pursue intensive intervention if the baby is born with health problems). During pregnancy, some parents choose to terminate babies diagnosed with Patau Syndrome due to the generally poor prognosis and the desire to not prolong the grief of the loss. Others continue the pregnancy due to beliefs against abortion or because they feel they would rather have some time with the baby even if it turns out to be short. The same applies to babies diagnosed after birth -- some parents choose comfort care only, whereas others opt for intensive medical interventions even though the chances appear slim that the baby will survive infancy.

If your baby has been diagnosed with Patau Syndrome, you may be having any number of emotions from grief to anger to numbness to simply feeling overwhelmed. It's fine to take your time and process the situation before moving forward and making decisions or plans. There is no "right" way to feel and no single "correct" course of action to take with these diagnoses. You have to do whatever you feel you will be most able to live with, and the answer is different for everyone.

Regardless of what you decide, it is fine to grieve the loss of the baby you were expecting to have. It can be helpful to join support groups for parents of babies with Patau Syndrome or other serious chromosomal disorders.


Patau Syndrome. National Library for Health. Genetic Conditions Specialist Library. Accessed: March 2, 2009. http://www.library.nhs.uk/geneticconditions/viewresource.aspx?resID=93804

Trisomy 13 - Genetics Home Reference. National Library of Medicine. Accessed: March 2, 2009. http://ghr.nlm.nih.gov/condition=trisomy13

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