What is NIPT? Advantages of NIPT over Traditional Prenatal Screening

What is NIPT?

Non-Invasive Prenatal Testing (NIPT) is a highly accurate prenatal screening test analyzing cell-free fetal DNA (cff-DNA), which originates from the placenta and circulates in the mother’s blood. This test assesses the risk of chromosomal abnormalities in the fetus without the need for invasive procedures.

Medical DIAG Center’s NIPT is performed using NIFTY®, a pioneering advancement technology developed by BGI Genomics, one of the world’s leading biotechnology corporations specializing in genomic sequencing and genetic analysis. NIFTY® has been validated through the largest global clinical study with over 145,000 samples ensuring exceptional accuracy and reliability.

As of 2024, NIFTY® has been chosen by more than 15 million pregnant women across 100+ countries. With an extremely low false-positive rate, it significantly reduces the risk of unnecessary amniocentesis and minimizes anxiety during pregnancy. This solidifies NIFTY® as a safe and precise prenatal screening solution without the need for invasive intervention.

Using just a small maternal blood sample, the NIPT test leverages Whole Genome Sequencing (WGS) – a breakthrough application of Next-Generation Sequencing (NGS) – to analyze fetal DNA. This allows for the early detection of over 100 chromosomal abnormalities as early as the 10th week of pregnancy.

Note: NIPT is a screening test, not a diagnostic tool. If the results indicate a high risk, pregnant women should consult a specialist for further evaluation and confirmatory diagnostic procedures, such as amniocentesis or chorionic villus sampling.

Prevalence of Chromosomal Abnormalities in Fetuses

NIPT was developed to detect early chromosomal abnormalities that could potentially impact the comprehensive development of the fetus. Therefore, NIPT is an essential test in prenatal healthcare, helping to minimize the risk of chromosomal abnormalities in the fetus.

The rate of chromosomal abnormalities in the fetus is remarkably high, according to various studies conducted in Vietnam and globally.

Each year, approximately 41,000 children are born with congenital anomalies in Vietnam. While there is no comprehensive national study on the prevalence of chromosomal abnormalities in fetuses, specialized studies conducted in 2017 indicate that the incidence of these abnormalities in Vietnam* is relatively high compared to global rates.

• The rate of Down syndrome in children in Vietnam is 1.25/1,000, compared to the global rate of 1.43/1,000.
• The rate of Edwards syndrome in children in Vietnam is 1/6,000, compared to the global rate of 1/8,000 – 1/3,000.
• The rate of Patau syndrome in children in Vietnam is 1,233/8,000, compared to the global rate of 1/8,000 – 1/5,000.

Advantages of NIPT over Traditional Prenatal Screening**

The primary goal of NIPT is to enable early and highly accurate detection of chromosomal abnormalities in the fetus. NIPT results provide valuable support for expectant mothers, families and obstetricians in making informed and timely decisions to ensure a healthy pregnancy.

1. Over 99% – Superior detection accuracy

NIPT offers greater than 99% accuracy, significantly surpassing traditional screening methods such as Double Test (80%) and Triple Test (85%).

2. Only 0.1% – Extremely low false-positive rate

NIPT ensures 999 out of 1,000 positive cases are truly abnormal. This dramatically improves the detection rate for chromosomal disorders compared to Double Test (~7%), particularly for common genetic conditions like Down syndrome, Edwards syndrome and Patau syndrome.

3. Early detection from the 10th week of Pregnancy

NIPT allows for early genetic screening as early as week 10, much earlier than Double Test (weeks 11 – 13) and Triple Test (weeks 16 – 20).

4. Comprehensive screening for over 100 chromosomal abnormalities

NIPT can screen for over 100 chromosomal abnormalities in a single blood draw, providing a much broader scope of detection compared to Double Test (3 abnormalities) and Triple Test (3 abnormalities).

5. Single blood sample – No need for additional Karyotyping

With just one blood sample, NIPT can screen for a wide range of chromosomal abnormalities, including autosomal and sex chromosome aneuploidies, as well as microdeletions and duplications, with higher efficiency than traditional tests.

6. Non-invasive and Safer than invasive procedures

NIPT is a non-invasive test that requires only a maternal blood sample, eliminating direct intervention in the fetus. Unlike amniocentesis or chorionic villus sampling, NIPT does not pose risks of amniotic fluid leakage, infection or miscarriage, making it a safer alternative for prenatal screening.

Candidates for NIPT

NIPT is recommended for all pregnant women of all ages, particularly those over 35 years old, as well as those who wish to screen for chromosomal and genetic abnormalities in the fetus at an early stage.

According to recommendations from the World Health Organization (WHO), the UK National Health Service (NHS), and the Vietnamese Ministry of Health, NIPT is particularly advised in the following cases:

Medical history considerations:

• Pregnant women with a history of multiple miscarriages, stillbirths, or preterm labor.
• Pregnant women who have previously given birth to a child with chromosomal abnormalities.
• Pregnant women with a family history of chromosomal disorders.

Conditions affecting the ability to undergo prenatal tests:

• Pregnant women who cannot undergo invasive prenatal testing due to high risk of miscarriage, increased bleeding tendency, current fever or chronic infections, etc.
• Pregnant women who missed the optimal timeframe for traditional biochemical screening tests (Double Test, Triple Test).
• Pregnant women working in hazardous environments or exposing to chemicals.

Abnormal screening results:

• Pregnant women with abnormal ultrasound findings.
• Pregnant women with high-risk results from traditional biochemical screening methods (Double Test, Triple Test).

Pregnancy type:

• Pregnant women carrying singleton or twin pregnancies.
• Pregnant women who conceived through assisted reproductive technologies, such as IVF or IUI.

In special cases, NIPT is also suitable for certain groups of pregnant women who meet the accompanying conditions:

• Pregnant women who have received a blood transfusion or an organ transplant at least 4 months prior.
• Pregnant women diagnosed with Vanishing Twin Syndrome, provided that: (1) the vanished twin was lost before 8 weeks of gestation, (2) the NIPT test is conducted at least 8 weeks after the twin’s disappearance.

Latest ACMG Guidelines on NIPT

The American College of Medical Genetics and Genomics (ACMG) has issued updated recommendations to enhance the effectiveness of early detection of fetal genetic abnormalities.

• NIPT is recommended for screening for Trisomy 21, Trisomy 18, Trisomy 13 in singleton and twin pregnancies, as a preferred alternative to traditional screening methods like Double Test and Triple Test.
• NIPT is recommended for fetal sex chromosome aneuploidy screening in singleton pregnancies.
• NIPT is recommended for DiGeorge syndrome to all pregnant women.

Limitations of NIPT

NIPT is a screening test, not a diagnostic test. If NIPT results indicate a high risk for chromosomal abnormalities, pregnant women should consult a specialist for further diagnostic testing to confirm the findings, such as amniocentesis or chorionic villus sampling.

Frequently Asked Questions

Why should both Ultrasound and NIPT be performed?

Ultrasound imaging is crucial for monitoring fetal development, but it cannot detect chromosomal abnormalities. Combining NIPT with ultrasound provides a more comprehensive risk assessment for fetal chromosomal abnormalities with high accuracy.

Is NIPT 100% accurate?

NIPT is a screening test, not a diagnostic test. Since NIPT analyzes placental DNA fragments, false-positive results may occur due to placental mosaicism and false-negative results may arise if mosaicism is confined to the fetus.

Although NIPT has a high accuracy rate (>99%), confirmatory diagnostic tests are recommended for definitive diagnosis.

Can NIPT detect all genetic disorders?

No. NIPT can only screen for specific chromosomal-related disorders. It does not detect all genetic diseases or congenital defects.

Can NIPT be performed for pregnancies with three or more fetuses?

No. NIPT is only available for singleton and twin pregnancies.

When can a pregnant woman take the NIPT test?

NIPT can be performed as early as the 10th week of pregnancy.

What should a pregnant woman do if NIPT results indicate high risk?

When an NIPT result indicates a high risk for a chromosomal abnormality, it does not mean that the fetus definitively has the condition.

NIPT is a screening test, not a diagnostic test. Therefore, pregnant women should consult an obstetrician for further evaluation and may be advised to undergo confirmatory diagnostic tests such as amniocentesis or chorionic villus sampling.

Is a low-risk NIPT result completely reassuring?

A low-risk result means that the likelihood of fetal chromosomal abnormalities is very low. However, it does not guarantee that the fetus is completely free from chromosomal abnormalities. Pregnant women should continue regular prenatal check-ups, follow the recommended screening and diagnostic tests as advised by the obstetrician.

Can NIPT Twins identify chromosomal abnormalities for each individual fetus?

No. The fetal DNA in maternal blood comes from both fetuses mixed together. A positive result only indicates that at least one fetus may have aneuploidy but not which one. Even if individual aneuploidy detection were possible, it may not significantly change clinical decision-making, as the next step is invasive testing on both fetuses (e.g., amniocentesis or CVS) to confirm the diagnosis and determine which fetus is affected.

If invasive testing confirms aneuploidy, the clinical decision will be based on the result, not on whether NIPT Twins could have pinpointed the specific fetus initially.

The final decision will depend on several factors, including zygosity whether the twins are monochorionic (one placenta) or dichorionic (two placentas). The precise identification of the affected fetus also depends on invasive testing, the severity of the detected aneuploidy, potential pregnancy risks, and the parents’ wishes regarding continuation or selective reduction.

In monochorionic twins, a confirmed diagnosis in one fetus means both are affected, limiting management options.

In dichorionic twins, selective reduction of the affected fetus may be a possible option, depending on medical feasibility and ethical considerations.

NIPT Testing with NIFTY® Technology at DIAG Medical Center

The NIPT utilizes NIFTY®, which ensures high accuracy and efficiency. This advanced screening technology is built on the largest global clinical study, analyzing over 145,000 samples collected from more than 500 medical centers between 2011 and 2013**.

The NIPT offered at Medical DIAG Center enhances screening accuracy by reducing the false-negative rate, lowering the need for retesting by 50%, and improving the detection of chromosomal abnormalities. NIPT can identify over 100 chromosomal abnormalities, including autosomal aneuploidies, sex chromosome aneuploidies and rare microdeletions/duplications.

The performance of the NIFTY® screening method was recognized in the New England Journal of Medicine (NEJM) in 2015, where it was noted for having the lowest false positive rate among NIPT tests. This provides reassurance for doctors when recommending the test***.

Learn more about NIPT testing at DIAG: https://diag.vn/panel/goi-xet-nghiem-nipt/

Source:

* Ministry of Health and Viet Nam Population Authority statistics 2017

** Zhang H et al., Non-invasive prenatal testing for trisomies 21, 18 and 13: clinical experience from 146,958 pregnancies. Ultrasound Obstet Gynecol. 2015 May;45(5):530-8. doi: 10.1002/uog.14792. Epub 2015 Apr 8. Erratum in: Ultrasound Obstet Gynecol. 2015 Jul;46(1):130. PMID: 25598039

*** Cheung SW, Patel A, Leung TY. Accurate description of DNA-based noninvasive prenatal screening. N Engl J Med 2015;372:1675-7. DOI: 10.1056/NEJMc1412222