To find out which NIPT test is the best for you, first we have to understand what NIPT is.
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NIPT stands for Non-Invasive Prenatal Testing. These high-end tests are performed during pregnancy and before birth to screen for certain chromosomal abnormalities such as Down’s syndrome. They are performed like a typical blood test where a sample of the mother’s blood is drawn from the arm. They are completely safe and do not involve any kind of instrument being inserted into the pregnancy or involve risk of miscarriage.
What are NIPT tests?
NIPT is a genetic test that can provide information about the risk of certain chromosomal abnormalities in a developing fetus. NIPT tests are performed during pregnancy and are considered a safer alternative to invasive prenatal diagnostic procedures such as amniocentesis or chorionic villus sampling (CVS).
What is a screening test?
Screening tests are used to find people at a higher chance of a health condition. This means they can get earlier, potentially more effective treatment or make informed decisions about their health. It can be helpful to imagine screening as putting people through a sieve. Most people pass straight through but a small number get caught in the sieve. The people caught in the sieve are those considered to have a higher chance of having the health condition being screened for.
How does the NIPT test work?
NIPT works by examining cell-free DNA (cfDNA) fragments present in the mother’s bloodstream. These fragments originate from the placenta and contain genetic information from the developing fetus. The main steps involved in NIPT are as follows:
1. Sample Collection
The healthcare provider collects a blood sample from the pregnant woman, usually through a standard blood draw. This sample contains the cfDNA fragments.
2. cfDNA Extraction
The laboratory isolates and extracts the cfDNA from the blood sample. This process involves separating the cfDNA from other components in the blood, such as red and white blood cells.
The extracted cfDNA undergoes high-throughput sequencing. This sequencing technique allows the laboratory to analyze and determine the genetic information contained within the cfDNA fragments.
4. Data Analysis
The sequencing data is then analyzed using advanced bioinformatics algorithms. The laboratory compares the genetic information obtained from the cfDNA fragments to a reference genome to identify any chromosomal abnormalities or genetic variations.
5. Reporting Results
Once the analysis is complete, the laboratory generates a report that provides information about the specific chromosomal abnormalities screened for, such as trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome). The report typically includes the risk assessment or probability for each condition.
A few important points
It’s important to note that NIPT does not directly analyse the fetal DNA itself but analyses the cell-free DNA fragments derived from the placenta, which carry similar genetic information. The test relies on the fact that these fragments can be detected and analyzed in the mother’s bloodstream.
It’s also worth mentioning that different NIPT technologies may have variations in the specific laboratory procedures used, but the general principles remain consistent. Additionally, NIPT’s specific details and performance characteristics can vary depending on the test provider and the region where the test is conducted.
It’s recommended to consult with healthcare professionals or genetic counsellors for detailed and accurate information about the specific NIPT test being used and the procedures involved.
Advantages of NIPT Tests
NIPT are non-invasive
These tests do not pose any risk of harm to the fetus or the mother. It involves a simple blood draw from the pregnant woman, usually around 10 weeks or later into the pregnancy.
NIPT screens for specific chromosomal abnormalities, such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), Patau syndrome (trisomy 13), and certain sex chromosome abnormalities. The test analyses cell-free DNA (cfDNA), which are basically fragments from the placenta that circulate in the mother’s bloodstream.
NIPT has a high detection rate for the conditions it screens, typically exceeding 99% for Down syndrome. However, it’s important to note that NIPT is only a screening test, not a diagnostic one. Diagnostic tests provide a definitive diagnosis, whilst screening tests are not. Positive NIPT results are often confirmed through invasive diagnostic procedures.
NIPT tests can be performed from as early as 9 weeks in the pregnancy, providing couples with information about their risks earlier than other conventional tests, such as the combined screening test offered in the NHS in the UK.
Limitations of NIPT Tests
They are not definitive and do not provide a diagnosis. A positive NIPT result doesn’t guarantee that the fetus has a chromosomal abnormality, and false positives and false negatives can occur.
NIPT primarily focuses on chromosomal abnormalities and cannot detect all genetic or structural abnormalities in a fetus. It’s specifically designed to assess the risk of certain conditions caused by an abnormal number of chromosomes.
In the UK, NIPT tests are typically not available on the NHS and are only available privately. They can be quite expensive with prices ranging considerably depending on the test provider and the private clinic you perform the test.
Alternatives to the NIPT test
All expectant mothers in the UK are offered the combined test as part of their NHS maternity care. The combined test is also a screening test for Down’s syndrome and is performed from 10-13 weeks. The combined test is a fantastic test, but it is not as sensitive as NIPT tests are. The combined test does not look at the cell-free DNA (cfDNA) from the baby but instead looks at a combination of other things, including some maternal hormones, maternal age and the nuchal translucency measurement from the ultrasound scan.
Things to consider before having the NIPT test
NIPT tests are typically recommended for pregnant women who have an increased risk of chromosomal abnormalities based on factors like maternal age, previous test results, family history, or ultrasound findings. It’s important to discuss the benefits, limitations, and potential risks of NIPT with a healthcare professional before deciding to undergo the test.
To read more information from the Gov UK website on screening tests – please click here.