Genetics Northern California

Trisomy 13

What is trisomy 13?
How common is trisomy 13?
What causes trisomy 13?
How is trisomy 13 diagnosed?
Can trisomy 13 be diagnosed during pregnancy?
How is trisomy 13 treated?
Where can I get more information about trisomy 13?

What is trisomy 13?
Trisomy 13, also called Patau syndrome, is a genetic condition that causes birth defects and developmental disability. Many babies with trisomy 13 are miscarried, stillborn or survive just a brief time after birth. However, some children with trisomy 13 live longer.

Medical concerns in trisomy 13
    Newborns with trisomy 13 often struggle to breathe and feed properly and usually need extra time in the hospital. Common medical problems include:
        - Heart defects 
        - Brain or spinal cord abnormalities 
        - Small or poorly developed eyes 
        - Extra fingers or toes 
        - An opening in the lip (cleft lip) or the roof of the mouth (cleft palate) 
        - Low muscle tone 
        - Umbilical hernia (omphalocele)
        - Seizures 
        - Kidney defects

Learning in trisomy 13 
    Children with trisomy 13 have significant developmental delays. However, some children do reach early milestones, such as smiling and responding to family members.

How common is trisomy 13?
Trisomy 13 is a rare chromosome abnormality, affecting about one in every 5,000 to 10,000 babies.

Trisomy 13 karyotypeWhat causes trisomy 13?
Trisomy 13 is caused by an extra chromosome in a person’s cells. Normally, there are 46 chromosomes in human cells. The chromosomes come in pairs, so usually there are two of each different chromosome. This includes two copies of chromosome 13 (one from each parent). Most children with trisomy 13 have three separate copies of chromosome 13 (instead of the usual two) in every cell of the body. This type of trisomy 13 happens randomly and does NOT run in families. Trisomy 13 is more likely as a woman ages, but it can happen in mothers of any age.

It is possible to have some cells with trisomy 13 and some cells with the usual number of chromosomes. This is called mosaic trisomy 13. Individuals with mosaic trisomy 13 have the same medical concerns as someone with full trisomy 13, but there is a wider range of outcomes in these children. It is also possible to have trisomy 13 caused by a change in the way the chromosomes are arranged. One chromosome 13 may be combined with a different chromosome. This is called a translocation. Rarely, translocations can be inherited from a parent who does not have trisomy 13. If you have a family history of trisomy 13 you can talk with a genetic counselor to learn your chance of having a child with the condition.

How is trisomy 13 diagnosed?
Trisomy 13 is diagnosed by studying the baby’s chromosomes in a laboratory. This can be done by a prenatal diagnostic test or a blood test after birth. Trisomy 13 may be suspected at birth based on some common physical findings in babies with this condition. A blood test is needed to confirm the diagnosis. Chromosome testing will also show if other family members may be at higher risk for Trisomy 13.

Can trisomy 13 be diagnosed during pregnancy?
Trisomy 13 can be diagnosed during pregnancy with a prenatal diagnostic test, either chorionic villus sampling (CVS) or amniocentesis. These tests examine the chromosomes of the developing baby.

Prenatal screening tests can tell you about your risk for trisomy 13, but they do not tell you if a baby has the condition. Screening tests might include a blood test on the pregnant woman or an ultrasound of the developing baby. If a screening test shows a higher risk for trisomy 13, a diagnostic test is offered to find out if the baby has it.

How is trisomy 13 treated?
There is no cure for trisomy 13, but medical treatment can address some of the related problems. Surgery can improve comfort and life expectancy in some cases. Most states have programs that help families care for children with special needs. There are also trisomy 13 support groups.

When a baby is born with trisomy 13, parents may be asked to make some tough decisions about the baby’s medical care. You can receive help and support in this process from the baby's doctor, the nursery social worker, hospital chaplain and your genetic counselor.

Where can I get more information about trisomy 13?

General information 
Genetics Home Reference: Trisomy 13 - General information about trisomy 13 provided by the National Library of Health. Also includes links to related sites.

Parent Support Resources 
SOFT - Support Organization for Trisomy 18, 13 and Related Disease – Support group for parents who have had or are expecting a child with a chromosome disorder (especially trisomy 13 and trisomy 18). Participating parents are strong advocates for their children and emphasize the positive aspects of raising a child with a trisomy condition.

Last reviewed: December 19, 2017
Last updated: December 19, 2017
Reviewed by: Kimberly Barr, LCGC