Trisomy 13

Diagnosis and Testing

How do babies get tested for Trisomy 13?

There are a few types of genetic tests that can diagnose trisomy 13. After birth, trisomy 13 can be diagnosed by examining the cells from a blood sample. The basic test is called a karyotype, where the chromosomes are counted and examined in a laboratory called a cytogenetic lab. This test takes about 7-10 days for a result. A rapid, preliminary test for trisomy 13 is called fluorescence in situ hybridization or FISH. This test uses a brightly colored probe to quickly count the number of copies of a given chromosome and can provide an early result in 2-3 days. A newer way to examine genetic material is called a chromosome microarray, which looks for extra or missing pieces of genetic material. This test can also be used to diagnose trisomy 13.

Before the baby is born, these same tests can be completed on a sample of amniotic fluid, which contains skin cells from the baby. A physician would use a procedure called an amniocentesis to withdraw a small amount of fluid from around the baby for genetic testing. Another way to use these tests during pregnancy is chorionic villus sampling (CVS). In this procedure, a physician obtains a small sample of the placental tissue. The placenta and the baby come from the same fertilized egg, so performing genetic testing on the placental cells should give the same results as testing the baby.

Curr Probl Pediatr Adolesc Health Care. 2012 Mar;42(3):47-73. doi: 10.1016/j.cppeds.2011.10.004.Advances in whole-genome genetic testing: from chromosomes to microarrays.Crotwell PL1, Hoyme HE.

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