Details of Non-invasive prenatal testing

What is Noninvasive prenatal testing?

Non-invasive prenatal testing: DNA fragment testing, fertility, IVF, Surrogacy

Read Also: Frequently Asked Questions related to surrogacy

Noninvasive prenatal testing (NIPT) is a screening test to determine the risk genetic abnormalities of the fetus. In this test method, a small fragment of DNA is analyzed, which is circulated in the maternal blood. This small fragment of DNA is floated freely instead of staying within the cellular nucleus. This cell-free DNA fragments contain almost 200 DNA base pair and release in the bloodstream after breaking down cellular content of death cell.

How Noninvasive prenatal testing works?

During pregnancy, a uterine tissue placenta is a connection between fetal and maternal blood supply.  Pregnant women’s blood contains a mix of cell-free DNA (cfDNA) fragments, which derive from the maternal cell and placental cell. The shedding of placental cells recurrently appears in the maternal bloodstream during the whole gestational period.  The placental cells containing DNA are usually alike with fetus cellular DNA. Therefore, testing of cfDNA obtained from placenta assist to early detection of fetal genetic abnormality without hurting the fetus.

What diseases can be identified through noninvasive prenatal testing?

Noninvasive prenatal testing is conducted to check the chromosomal abnormalities, which may be associated with one extra or lacking a chromosomal copy. This screening test can identify Down syndrome, which occurs due to an excess copy of chromosome 21 or 18 or 113 or missing or add up one copy of a sex chromosome (X and Y chromosome). The test result accuracy can vary depending upon the underlying disorder.

The advancement of technology improves the ability of NIPT. Previously, this test could only identify the alteration of a single gene. But currently, multiple genetic disorders can be identified through NIPT. Nowadays, it is used for screening the additional chromosomal disorders, which are usually associated with deletion or duplication of the chromosome.

Pros and cons of NIPT

This test is a non-invasive process. In this test, only maternal blood require to withdraw for analyzing purpose. No harm associated with fetal growth. This test report does not give a definite result. However, this can screen the genetic abnormality of a developing fetus and gives the answer to the fetal genetic condition.  This test can only identify the risk associated with the genetic condition. In certain cases, this test report can also give a false result.  For example, the test report showed an increased risk of fetal genetic abnormality, but the fetus is not affected.  Whereas in some cases, it shows a decrease in the risk of genetic abnormality, but fetus actually affected with the condition. This fluctuation occurs may due to the collected blood contains both maternal and fetal cfDNA. It can also detect the genetic condition of the mother. Therefore, the test report is not the ultimate determination of the fetal genetic condition.

How to get an accurate result?

To obtain the perfect result, it is necessary for maternal blood should contain sufficient amount of fetal cfDNA. Placental blood is the only source of fetal cfDNA. To obtain an accurate result, more than 4% of the fetal fraction must be present in maternal blood. This is possible only after the 10th week of pregnancy. Low fraction of fetal blood is one of the primary reason for the faulty result of the test report. There are multiple factors which influence low fraction of fetal blood, including early testing, maternal obesity, erroneous sampling, and fetal abnormality.    

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