Noninvasive prenatal testing

Overview:

Non-invasive prenatal testing (NIPT) is an advanced test done in pregnancy to check for chromosomal abnormalities. It is a revolutionary screening method to detect chromosomal abnormalities. It is also called noninvasive prenatal screening (NIPS) or cell-free DNA screening (cfDNA). It analyzes fetal FNA found in the mother’s blood and identifies chromosomal abnormalities in the fetus.

NIPT determines the amount of risk of developing chromosomal abnormalities in the fetus. NIPT does not diagnose the condition, but it estimates the likelihood of having chromosomal abnormalities as it is a screening test.

Mechanism of NIPT:

NIPT works on the principle of analyzing DNA fragments. The pregnant mother has a mix of DNA obtained from the fetus. This is derived from the fetus and is present in the placenta. The placenta connects the fetus tissue with the mother through blood vessels. DNA from the fetus sheds into the placenta which reaches the mother. This is called cell-free DNA (cfDNA). This cfDNA is similar to the fetus's DNA and is floating freely in the mother’s blood. These cfDNA are very small fragments of DNA. Analyzing this cfDNA gives information about the risk of development of chromosomal abnormalities in the fetus.

Necessity of NIPT:

Chromosomal abnormalities in the fetus are the major causes of stillbirths and births. These are also responsible for infants born with malformations. This can cause immense psychological stress in the parents.

Indications:

NIPT is indicated when it is suspected that a fetus may have a chromosomal abnormality. This is also advised when an ultrasound shows abnormalities in the fetus. It is also advised when an earlier screening of the pregnant mother shows abnormalities. Earlier NIPT was recommended to only high-risk individuals, but present recommendations suggest NIPT to all pregnant women.

NIPT detects chromosomal disorders that are caused due to abnormal chromosomes. The test typically is done as early as 10 weeks of pregnancy. This includes chromosomal disorders caused due to the presence of an extra chromosome or due to the absence of the actual number of chromosomes. These disorders include:

Downs syndrome (trisomy 21 – extra chromosome in 21)
Trisomy 18 (extra chromosome 18)
Trisomy 13 (extra chromosome 13)
Tetrasomy of 18p
Balanced chromosomal disturbances and unbalanced rearrangements
To detect microdeletion syndromes
Extra or missing copies of chromosomes X and Y like Turner syndrome, Klinefelter syndrome, and Triple X syndrome.
Genetic disorders are caused due to changes in single genes.
It is also indicated for psychological reasons of distress and anxiety.
NIPT is also indicated when there is immense pressure to have a healthy and perfect child.
It is also indicated when there is a family history of chromosomal abnormalities.
It is advised when there is a previously affected child
It is also indicated when there is a disadvantage of having procedure-induced abortion due to invasive screening tests.

Advantages:

NIPT is a non-invasive test that does not disturb the fetus. It does not pose any risk of harm to fetus or miscarriage. This test shows the risk of having chromosomal abnormalities is increased or decreased. It is accurate in detecting chromosomal abnormalities like trisomies. It has fewer false positive results with better traditional screening methods.

NIPT can also determine the fetal sex and paternity in the fetus much earlier than other traditional methods. It also determines the fetal rhesus D status that prevents unnecessary interventions in pregnant mothers. NIPT is widely accepted globally as a pregnancy screening method. This is an effective and reliable method of detecting chromosomal abnormalities. This is performed as early as 10 weeks in pregnancy giving an advantage of early detection of any abnormalities.

Before the procedure:

NIPT is a screening test of choice. It is when advised by a healthcare professional due to suspicion of abnormality in the ultrasound or any other tests.

During the procedure:

An individual is made to sit comfortably on the table such that the area where blood is to be drawn is accessible to the healthcare professional. Blood will be drawn from a vein by using a small needle after making the area aseptic. The required amount of blood is collected in a vial and sent to the lab for evaluation.

After the test:

One can continue daily activities after the test. The result values will be obtained after a few days. It will take at least 2 weeks for the results to be sent.

Interpretation of the results:

NIPT is a screening test that sends results based on the increased or decreased risk. Sometimes the results will be separate for each condition and sometimes overall risk will be obtained. No test results may indicate insufficient fetal DNA in the mother's blood or difficulty in identifying the fetal DNA. There is a 99% success rate of NIPT in detecting Down syndrome.

Drawbacks of NIPT:

NIPT success depends on the amount of fetal DNA found in the mother’s blood. The weight of the mother, the number of pregnancies, and surrogacy also play an important role in obtaining proper results. Fetal fraction is the amount of fetal DNA in the maternal blood that comes from the placenta. Its value should be above 4% for accurate results of NIPT. Any fetal fraction less than that can give abnormal results.

Conclusion:

NIPT is the first-tier screening test that detects chromosomal abnormalities in the fetus. It is a crucial test that detects the fetal DNA obtained from the mother’s blood. It helps the parents in making informed decisions and gives reproductive autonomy.