What is NIPT (New Prenatal Testing)?
NIPT (new type prenatal testing) , also known as non-invasive prenatal genetic testing, is a prenatal test that only requires a blood sample from the mother. Similar to blood samples taken during general health checkups, blood is taken from the mother’s arm with a syringe, so it is considered a testing method that causes very little direct invasion (damage) to the baby.
A mother’s blood contains fetal DNA. NIPT can detect the possibility of a baby having chromosomal abnormalities or a risk of congenital diseases from fragments of that DNA .
Conventional non-confirmatory tests such as maternal serum markers and combined tests could be performed from the 11th week of pregnancy onwards. However, Hiro Clinic’s NIPT test can be performed from around the 6th week of pregnancy (when pregnancy is confirmed by ultrasound), which means that it is possible to check the baby’s health condition earlier in pregnancy than with previous prenatal tests.
NIPT is a screening test (non-confirmatory test). It determines the risk of chromosomal abnormalities such as Down syndrome (trisomy 21) , Edwards syndrome (trisomy 18) , and Patau syndrome (trisomy 13) by determining whether the result is positive or negative. It is also said to be possible to find out the baby’s gender in addition to chromosomal abnormalities.
Like other prenatal tests, NIPT is not covered by insurance. Since the cost and conditions of the test vary depending on the NIPT facility, it is important to check the cost and conditions in advance.
Accuracy of NIPT (New Prenatal Test)
There are two standards for measuring the accuracy of chromosome testing: sensitivity and specificity.
The percentage of mothers who tested positive after giving birth is the “sensitivity.” The percentage of mothers who tested negative after giving birth is the “specificity.” In other words, the higher the sensitivity and specificity, the higher the accuracy of the test.
The accuracy of NIPT (non-invasive prenatal testing) for Down syndrome (trisomy 21) is said to be extremely high, with a sensitivity and specificity of 99.9% . For these reasons, compared to conventional prenatal testing using blood such as maternal serum markers, NIPT, which has high testing accuracy, can more accurately detect the number of abnormal chromosomes in a baby.
However, NIPT is a screening test (non-definitive test), so a definitive test such as an amniocentesis is required to more accurately check for chromosomal abnormalities in the baby.
What is amniocentesis?
NIPT (New Prenatal Testing) is a screening test (non-confirmatory test) to diagnose the possibility of a baby having a chromosomal abnormality. Therefore, if the NIPT test result is positive and you wish to receive a definitive test for a chromosomal abnormality, you will need to undergo an amniocentesis, which is a definitive test.
Amniocentesis is a test in which an ultrasound machine is used to puncture the mother’s abdomen and aspirate and collect amniotic fluid. The collected fluid (10-20ml) contains fetal cells, which are used to check for chromosomal and genetic abnormalities.
Since this test involves collecting amniotic fluid, it can be performed at 15-16 weeks of pregnancy when amniotic fluid accumulates. Also, like NIPT, this is a self-paid test that is not covered by insurance, so the cost varies depending on the medical institution.
Amniocentesis test method
There are three main types of amniocentesis testing:
<Testing method>
- G staining method
- FISH method
- Microarray method
①G staining method
The G-banding method is a method called Giemsa staining, and is the most common chromosome test. In the G-banding method, all chromosomes are stained to check for abnormalities in the number and structure of chromosomes. Since the test is performed using a chromosome microscope, very small deletions and mosaics that cannot be seen even with a microscope may not be detected.
②FISH method
The FISH method is a method to detect abnormalities by making certain cells of chromosomes glow with fluorescent dye. It is a method used to detect specific chromosomal abnormalities and to definitively diagnose large deletions or duplications of chromosomes, but it may not be possible to detect minute deletions. Another feature is that it produces results more quickly because it does not require culture operations.
3) Microarray method
Microarray literally means “fine arrangement” in Japanese. It is possible to observe minute changes in many chromosomes, and is considered to be a highly accurate method about 100 times that of G-banding and FISH.
Accuracy of amniocentesis
Amniocentesis is a definitive test that examines fetal cells contained in amniotic fluid. Its accuracy is very high, nearly 100%, but there are rare cases where a fetus diagnosed as having normal chromosomes by amniocentesis actually has Down syndrome (trisomy 21) .
Chromosomal abnormalities in Down’s syndrome (trisomy 21) are classified into standard type (trisomy type) in approximately 94%, translocation type in approximately 5%, and mosaic type in approximately 1%. Among these, mosaic type refers to the confirmation of both normal and abnormal cells, but if only normal cells are multiplied during the cell culture process, or if both types of cells are multiplied but only normal cells are detected, it may not be discovered until after birth that the baby is a chromosomal mosaic. In other words, in such cases, even if the amniotic fluid test diagnoses the baby as normal, the baby may be diagnosed with Down’s syndrome (trisomy 21) after birth.
The difference between NIPT (new type prenatal testing) and amniocentesis
There are three main differences between NIPT (new prenatal testing) and amniocentesis:
<Difference between NIPT (new type prenatal testing) and amniocentesis>
- When can the test be performed?
- Types of diseases that can be tested
- Probability of risk of miscarriage or stillbirth
Difference 1: When can the test be performed?
NIPT (New Prenatal Testing) can be performed from about the 6th week of pregnancy (when pregnancy is confirmed by ultrasound). On the other hand, amniocentesis is performed by collecting amniotic fluid, so it can only be performed after the 15th to 16th week of pregnancy when there is a sufficient amount of amniotic fluid. Therefore, if the NIPT result is positive, those who wish for a definitive diagnosis will need to undergo amniocentesis after the 15th to 16th week of pregnancy.
Nowadays, NIPT, which poses little risk of invasion (damage) to the fetus, is being used as a low-risk screening test (non-definitive test) before amniocentesis.
Difference 2: Risk of miscarriage or stillbirth
Amniocentesis involves inserting a needle into the mother’s abdomen to collect amniotic fluid to test for fetal cells. Therefore, there is a risk of miscarriage or stillbirth due to infection or bleeding caused by the needle, or leakage of amniotic fluid. The probability of miscarriage or stillbirth due to amniocentesis is said to be 1 in 300.
*The risk of miscarriage or stillbirth with chorionic villus sampling is 1/100
On the other hand, NIPT is a test that is performed only by taking blood from the mother. Therefore, it is said that the direct invasion (damage) to the fetus is very minimal.
NIPT (New Prenatal Testing) for the Health of the Fetus and Mother
NIPT (new type prenatal testing) allows early detection of the risk of congenital diseases caused by chromosomal abnormalities in the fetus. In addition, since chromosomal abnormalities in the fetus are one of the causes of miscarriage, it can also be said to be a test to protect the health of the mother. NIPT is less invasive (damage) to the fetus than previous prenatal testing, and is considered a highly accurate screening test (non-confirmatory test).
Hiro Clinic NIPT is a NIPT facility that respects the “right of mothers and their families to know.” We offer a variety of testing plans and options, from individual chromosome testing to testing of all chromosomes, as well as support from doctors and staff who are well versed in NIPT.
In addition, Hiro Clinic NIPT provides support for amniocentesis provided by affiliated testing institutions to reduce the financial burden for those who require amniocentesis. By paying the amniocentesis support fee of 3,300 yen (tax included) in advance, you can receive up to 200,000 yen in support for amniocentesis. For more information, please see ” About amniocentesis .”
“When should I start NIPT or amniotic fluid testing?” “I want to know the conditions for receiving NIPT.” Hiro Clinic NIPT receives many such inquiries. If you have any questions about NIPT, please contact Hiro Clinic NIPT , no matter how trivial. Let’s work together to find the best NIPT plan for the mother.
Article Editorial Supervisor
Dr Hiroshi Oka
NIPT specialist clinic, MD
Graduated from Keio University, School of Medicine
