Non-Invasive Prenatal Screening (NIPT)

NIPT has evolved to be the most powerful prenatal screening test as it bears the potential to identify if the unborn child/fetus is at risk for a number of genetic disorders like Down syndrome, Edwards syndrome, Patau syndrome, etc.

A simple blood test, the strength of NIPT lies in its ability of being non-invasive thus reducing the risk of miscarriage during testing to absolute nil coupled with the ability to screen for a number of disorders very early on in pregnancy; as early as in 10 weeks; much before other prenatal diagnostic tests. With an accuracy rate of over 95%, this DNA-based test works on the fetal genomic material or DNA present in the mother’s/maternal blood and thus becomes a very powerful assessor of developmental health of the unborn child. On an average the amount of circulating fetal DNA or cff-DNA as it is popularly known is about 10% of all circulating DNA in the maternal blood.

NIPT has emerged as an innovation that looks out for unbalanced chromosome counts (aneuploidy) and is ranked to be the most sensitive and accurate of the non-invasive tests. A healthy human has 23 pairs of chromosomes in each cell one set from each parents. It includes 22 pairs of autosomes and one pair of sex chromosome i.e XX in females and XY in males. Changes in the number as well as structure of these crucial genetic entity has been associated with a number of different developmental disorders including cancer.

The American Congress of Obstetricians and Gynecologists (ACOG) advises the doctors to discuss all screening options with the carrying women irrespective of the risk or age, and the choice to opt for the test remains personal. Counseling to understand the need is the key in NIPT to weigh potential benefits for a case-by-case basis.

What does NIPT screen for?

  • Down’s syndrome or Trisomy 21
  • Edward’s syndrome or Trisomy 18
  • Patau syndrome or Trisomy 13
  • Other chromosomal aneuploidies

Indications for NIPT

  • Increased maternal age
  • An abnormal ultrasound
  • Positive in first trimester by double marker test
  • Positive in second trimester screening by Triple or Quadruple marker test
  • IVF pregnancy involving a donor egg or treatment
  • Previous pregnancy with chromosomal aneuploidy

This non-invasive test can also be done to assess the general health of the early-stage foetus or to mitigate any concerns.

Contraindications for NIPT

  • History of recurrent miscarriages
  • Increased gestation age of the pregnant women

Though the above is predominantly perceived as cases not suitable for NIPT or not needing one, this simple test can be taken as per physician outlook and case-by-case necessity. This is because the test does not bear any inherent harm.

Steps involved in NIPT

  • Blood collection from the mother in specialized sample collection tubes
  • Separation of the cff-DNA (cell-free foetal DNA) from the blood
  • Sample preparation involving processing of the extracted cff-DNA to assess quality and quantity
  • NGS or Next-Generation Sequencing analysis of the cff-DNA
  • Data analysis using well-validated bioinformatics tools
  • Report generation
  • Report verification and release

All the above processes happen in a state-of-the-art laboratory replete with complete automation powered by the best of technologies and certified professionals.

Advantages of NIPT

  • This is the earliest prenatal test that acts a preclude to invasive tests in many cases by positively detecting only the high-risk cases for further amniocentesis or chorionic villi sampling
  • The inherent risk of miscarriage which comes with the invasive tests is avoided here
  • The expertise for sample collection is minimal

Limitations of NIPT

  • It is a screening test, and in case positive would still require confirmation by a diagnostic test as per physician recommendation
  • In case of twins or multiple pregnancies, the challenge arises in differentiating and identifying the fetal source of the cff-DNA in the maternal blood
  • The quantity of cff-DNA in the maternal blood can be influenced by many factors like the gestation age, BMI of the carrying mother, etc.
  • The result can have deep implications on the future course of action and hence one needs to be adequately prepared to handle the same

Technology in NIPT

Since NIPT involves analyzing the cff-DNA extracted from maternal blood, the proportion of which is roughly about 10% of all the circulating DNA, the sensitivity and accuracy of the technology becomes crucial to reduce the false-positives and negatives. The Next-Generation Sequencing (NGS) technology has emerged as a winner to effectively overcome the drawbacks of the conventional tests, thus adding great value to NIPT. Combination of a powerful bioinformatics solution with a high output next-generation genomic analysis platform make NIPT a great antenatal screening tool with no parallel.