Understanding Non-Invasive Prenatal Testing When You Are Expecting

Priya Kumar
7 minutes ago
3 min read

Image Credit: Freepik

What is Non-Invasive Prenatal Testing (NIPT)?

NIPT is a technique that relies on the analysis of cell-free fetal DNA (cff DNA) extracted from the blood of a pregnant mother. NIPT results offer valuable information about the genetic makeup of the unborn child. This technique has revolutionized the field of maternal and fetal medicine eliminating the risk of miscarriage associated with invasive procedures such as amniocentesis, chronic villus sampling, and umbilical cord sampling. In amniocentesis, the placental tissue is examined whereas in chronic villus sampling and umbilical cord sampling fetal tissue is examined.

Cell-free fetal DNA (cffDNA): The foundation of NIPT

Cell-free fetal DNA (cffDNA) was discovered in the late 1990s in the maternal blood circulation and forms the basis for NIPT. It originates from the placenta and is detected as early as four weeks of gestation making it a highly valuable biomarker for early detection of chromosomal abnormalities. Following childbirth, cffDNA is rapidly cleared and does not interfere with cffDNA in subsequent pregnancies.

What can NIPT detect?

The NIPT screens for the following chromosomal abnormalities

Downs Syndrome (Trisomy 21)
Edwards Syndrome (Trisomy 18)
Patau Syndrome (Trisomy 13)
Sex chromosomal (X and Y) disorders

A diploid human cell possess 46 chromosomes or 23 pairs of chromosomes one set inherited from the mother and one inherited from the father. Downs syndrome, Edwards Syndrome, and Patau Syndrome are a result of an extra chromosome 21,18, and 13 respectively. NIPT can also screen for unusual number of sex chromosomes.

When should a pregnant mother consider getting NIPT?

Fetal ultrasound along with biochemical testing of maternal blood is part of routine prenatal care in the United States as well as globally. These are very straight forward non invasive methods to know about the condition of the fetus. If an enhanced risk is suspected and warrants further clarification, NIPT is recommended. Based on the results of NIPT, further diagnostic testing may be recommended to get a definitive answer.

What are the advantages and limitations of NIPT?

Advantages:

The use of NIPT is advantageous in that the most common genetic conditions can be screened for using DNA derived from the placenta as early as ten weeks of gestation.
By harnessing the potential of advanced genetic testing technologies, incorporating NIPT in routine prenatal care has the potential for improved maternal and fetal outcomes.

Limitations:

Lack of proper understanding of NIPT results. It is important for expectant couples to understand that NIPT is a screening tool and that a positive test result requires confirmation through invasive testing.
The presence of false positives and false negatives results precludes the use of NIPT as a definitive test for diagnosing chromosomal abnormalities. For safe analysis and diagnosis, NIPT results are interpreted in conjunction with other prenatal tests including ultrasound and invasive testing.
Lack of adequate training among gynecologists, obstetricians, clinical geneticists, and genetic counselors on NIPT may contribute to inadequate knowledge and understanding of NIPT among patients.

What questions should expectant couples ask from their doctor about NIPT?

It is important that expectant couples ask questions from their doctor to educate themselves and to make informed choices.

Some questions to ask your doctor are:

How should I interpret my NIPT result?
What are the next steps if I have a positive NIPT test result?
Are there pre and post test genetic counseling services available?
What is the chance that my test result is false positive?

Conclusions and Future Directions

Despite the limitations, NIPT has the potential to be a highly reliable screening tool for chromosomal abnormalities. The technique also holds great promise for screening beyond the common chromosomal abnormalities and provide expectant parents with precise genetic information about their baby. The overall success of NIPT relies greatly on the education and training of healthcare providers so that they can provide adequate support to expectant parents and help them make informed choices.

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Assessed and Endorsed by the MedReport Medical Review Board