Trisomy 13, also known as Patau syndrome, is a rare chromosomal condition that presents with intellectual and physical disabilities because the individual has an extra copy of the 13th chromosome.
“All of our genetic information is packaged up in chromosomes to tell the body how to develop and grow,” said Victoria Ballard, genetic counselor with Marshfield Clinic Health System. “Typically, we have two copies of each chromosome, but individuals with Trisomy 13 have an extra copy of the 13th chromosome.”
Because of associated medical problems, many infants die within the first days of life. According to National Institute of Health (NIH), only 6-12% of children with this condition will live past their first year.
Ballard says, while there is some spectrum of severity in those with Trisomy 13, all affected children will need medical support throughout their life span. Due to the severity and rarity of Trisomy 13, it’s important for families to receive support during pregnancy and after childbirth.
“Ensuring that there’s a good care team in place to treat and help baby where they need help, is so important,” she said.
Signs of Trisomy 13
Trisomy 13 is often diagnosed in pregnancy or early infancy. Having an extra 13th chromosome can cause physical differences including:
- Structural differences of the heart and brain
- Cleft lip and palate
- Smaller or missing eyes
- Extra fingers or toes
- Kidney and bladder formation concerns
- Scalp differences.
Additionally, individuals have intellectual disability that is typically severe.
How to diagnose?
Ultrasounds or prenatal blood screenings may detect some of the birth defects that warrant further genetic testing for Trisomy 13.
Prenatal genetic testing for Trisomy 13 can be performed from a sample collected by an amniocentesis or chorionic villus sampling. Amniocentesis is a procedure where a small amount of amniotic fluid is sampled from the amniotic sac surrounding the baby. Chorionic villus sampling (CVS) samples chorionic villi from the placenta. Upon collection, these samples are sent off for the chromosomes to be analyzed.
These procedures can be done after a positive prenatal screening or if ultrasound detects something abnormal. Ballard explained that it is important to know what condition is being tested for with a small sample. If not detected during pregnancy, once the baby is born, genetic testing can confirm a diagnosis.
Trisomy 13 occurs in one of every 10,000 to 20,000 live births. However, this number may be inaccurate due to the number of miscarriages that go undiagnosed.
What causes Trisomy 13?
Trisomy 13 happens by chance. During conception of a baby, sometimes an extra chromosome slips through during the process. This error can happen sporadically and can occur more frequently as eggs within the body age.
“It’s nothing that a parent did or didn’t do,” Ballard said. “It’s just something that can happen.”
In rare occasions, Trisomy 13 can be inherited because of how the chromosomes bundle. Genetic counselors can review the parent’s chromosomes to determine if the condition was inherited, but the possibility is low.
“Typically, we would say there is a 1% or less risk of having a child affected with Trisomy 13,” Ballard said. “However, we know the risk increases with the pregnant parent’s age. As the eggs get older, there is a higher chance of errors occurring in the process of how chromosomes are organized within the egg cells which can be associated with this chromosomal condition along with others.”
Resources and support available
Support Organization for Trisomy (SOFT) is a website for families with children who have Trisomy 18, 13 and related disorders. The site has support groups, events and other resources to help parents get in touch with medical teams or other families in their area.
“Because this condition is so severe, medical care can be hard to find and I recommend this organization to help,” Ballard said. “Along with that, Facebook groups are a great way to connect with others. It can be really isolating, especially when it’s a rare condition. We are always here for support and information.”
To learn more about medical genetics services with Marshfield Clinic Health System, visit our website.
For more information about Trisomy 13, talk to your OB/GYN.
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