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Trisomy test - prenatal screening of congenital developmental disorders through mother’s blood sample

If you are over 35 years of age or if you have a positive biochemical screening test but you want to be more certain, you can have a Trisomy test made in this hospital. It is not covered by health insurance. Make an appointment via reception desk or your prenatal physician.  

Description of taking the samples and of the genetic examination    
The goal is to make non-invasive (blood) prenatal diagnostic test for fetal chromosome anomalies: trisomy chromosome 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome) tests. Trisomy (three copies) of chromosomes 21, 18 and 13 are the most common fetal chromosomal abnormalities manifested by multiple defects and mental disorders. Treatment of these abnormalities is not possible at present.


Description of proposed methods and procedures


The test is made by collecting about 10 ml of the mother’s blood. In about 3% of cases, the sample collection must be repeated because of insufficient fetal DNA concentration in the maternal blood. Blood is taken by a needle after disinfecting the area. The samples will be kept in Cell - Free DNA STRECK test tubes and slightly stirred (eight to ten times), or plasma or DNA may be extracted from the sample and frozen. Then the blood, plasma or DNA samples will be sent to the lab. The results of non-invasive prenatal test is to estimate the risks of fetal trisomy abnormality by the so called "aneuploidy", the presence of  an abnormal number of chromosomes, calculated from some chromosome sections by the "new generation sequencing", combined with bio-informatic analysis of the results. Prenatal non invasive tests bear no risks of spontaneous miscarriage or infection, are very precise, revealing more than 99% cases of fetal abnormalities. The test results will be ready in five workdays.

The risks related with unexpected findings affecting the patient and her genetic relatives

Only rarely, a bruise may develop at the puncture site by a needle stick, and quite exceptionally, inflammation may occur after taking blood samples.

Recently published information has proven efficiency of the test in 99.91% of trisomy 21, 98.79% of trisomy 18, and 98.7% of trisomy 13. However, there is still, although quite small, possibility of false negative test results On the other hand, positive results must be corroborated by invasive Chorionic Villus Sampling (CVS) or amniocentesis (AMC).
The test result may be distorted in case of maternal chromosome anomaly, if the test is made at an early stage of pregnancy when there is insufficient fetal free DNA in the maternal blood, in cases of multiple pregnancies, or if the fetus has a rare combination of chromosome anomalies (for example. chimerism, microduplication, microdeletion). The test results may also be distorted by another person’s DNA where the mother received transfusion or transplantation of stem cells.

Information on possible limitations for your habitual way of life, ability to work, treatment regime, and on proper preventive measures


There are no limitations after blood taking. The test is non invasive, and therefore there will be no limitations for your habitual way of life.