Prenatal Tests: Safe, Fast, and Reliable

What information can we get from non-invasive prenatal tests? In this article, we'll tell you their usefulness, the indications, and if they're safe.
Prenatal Tests: Safe, Fast, and Reliable

Last update: 06 October, 2021

Non-invasive prenatal tests (known by its acronym in English as NIPT), are blood tests that can be performed in pregnant women from week 10 of gestation. They make it possible to detect chromosomal, genetic, or physical abnormalities in the fetus through a blood sample taken from the arm of the future mother.

It’s a state-of-the-art test that’s been perfected in recent years. It provides important information on countless diseases that can go unnoticed in traditional routine monitoring of pregnancy.

Are prenatal tests invasive?

These tests are safe and non-invasive, which means that they don’t pose any risk to the fetus or the mother. With the traditional analytical screenings that doctors carry out in the routine follow-up of pregnancy, sometimes there are parameters that may be out of place and that later require the performance of an amniocentesis.

The latter consists of extracting a small amount of amniotic fluid after a minimal puncture at the woman’s abdominal level. Although this technique is safe if doctors perform it correctly, it’s not without risks.

At the same time, with non-invasive prenatal tests, the risk is lower. They don’t pose any type of danger and improve the percentages of precision when detecting chromosomal alterations.

To carry out these tests, doctors only need to extract blood from the mother’s arm, which they do with any other routine analysis. This makes it a completely safe test that offers very valuable information about the development of the fetus.

The explanation of its usefulness is simple. The mother’s blood contains cells and DNA fragments from the fetus, which circulate after it’s crossed the placenta.

Therefore, the study of maternal blood makes it possible to access the genome of the fetus with laboratory techniques. This, without having the need to extract amniotic fluid, which can pose a risk.

A doctor performing prenatal screening.

A laboratory will process the blood and separate the genome of the fetus from that of the mother.

What information do I get from non-invasive prenatal tests?

There are several types of non-invasive prenatal tests on the market. The most basic ones detect Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13), with a sensitivity close to 100%.

With this type of test, we can rule out these syndromes, due to their high reliability. In addition, we can do it without risks for the mother or the baby.

At present, the diagnostic options have increased, as we can observe duplications or deletions in the chromosomes, in addition to the fetal sex. Therefore, the list of diseases that a prenatal test is capable of ruling out or confirming has expanded.

Among the detectable diseases, we can mention the following:

Depending on the type or brand of test, the reporting of the results may be different. Interpretation is generally as follows:

  • Low risk: The fetus is fine. The mother’s blood is free of alterations in the fetal DNA, so the probability that the child suffers from chromosomal abnormalities is practically non-existent.
  • High risk: When studying the fetal DNA, experts conclude that there’s a possibility that the baby will be born with genetic problems or even that the pregnancy won’t come to fruition. Due to its high reliability, the false positive rate is quite low, so the result is very indicative. In these cases, there’s the possibility of expanding the genetic study, either with amniocentesis or with a chorionic biopsy.
  • Failed result: In very few cases, in the laboratory, it’s not possible to separate or distinguish the genome of the fetus from that of the mother, so a new blood extraction will be necessary in order to perform a correct analysis and interpretation.

What’s the importance of performing non-invasive prenatal tests?

For the peace of mind of couples expecting a baby, it’s good to know that routine pregnancy control that’s carried out on a regular basis is correct. This involves family doctors, midwives, and gynecologists. The physical examination, laboratory tests, cultures, and ultrasounds provide very useful information that’s protocolized by international entities, such as the World Health Organization (WHO).

However, there are situations that could benefit from a more exhaustive study, as there’s a greater risk of presenting a genetic alteration. Undoubtedly, when the pregnant woman is more than 35 years old, this is one of the most relevant risk factors for the fetus to present an abnormality.

Also, in couples who’ve already had a child with these problems or if there’s a history in close family members. All of these could be reasons to expand the study using these non-invasive tests. The results are much more reliable than the combined screening that women undergo at the end of the first trimester.

In cases of repeat miscarriages, this type of testing could also be justified. Women can have it done from week 10 of pregnancy, so the diagnosis is advanced.

In obese women, you have to wait a little longer, until week 14. It will be from that moment when the amount of fetal DNA in your blood is sufficient to be able to carry out the test.

The advantages of prenatal tests

There are several advantages to prenatal tests, which we can summarize in the following:

  • They reduce the number of amniocenteses. They confer greater security for both mother and baby.
  • Early detection, since they can take place from week 10.
  • They only require a blood sample from the mother, without requiring prior preparation. It’s a simple test.
  • They detect the most common syndromes and identify fetal sex.
  • The false positive and false negative rate is less than 0.5%. It’s a reliable test.
  • Results are available in just 8-10 days, so it’s considered fast.

Can prenatal tests detect Down syndrome?

If you’ve read this article to the end, you will already know the answer: Yes. One of the diseases that non-invasive prenatal tests detect is Down syndrome, whose alteration is identified as a trisomy on chromosome 21.

People with this disorder often have intellectual and developmental disabilities that can range from mild to moderate. In addition, specific physical features are characteristic. Children with Down syndrome are more likely to suffer from decreased sight and hearing, as well as disturbances in the heart.

With prenatal tests, it’s possible to reduce the unnecessary concern that traditional chromosomal disease screening produces. It also solves the false sense of security of the latter.

When a traditional biochemical screening is performed, out of every 20 women who test positive for Down syndrome, only 1 will conceive a baby with it. Furthermore, out of every 20 women who conceive a baby with Down syndrome, only 3 will be negative by traditional biochemical screening. For the detection of Down syndrome, non-invasive prenatal tests have an accuracy that’s close to 100%.

Get advice on non-invasive prenatal tests

Now you know about this technique and you can make the relevant consultations with your GP. Ask them if this test is necessary and what benefits you could obtain. Remember that it’s a safe and reliable option that continues to improve to offer more and more accurate data.

We thank SAVIA for its collaboration in providing information for the realization of this article.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Recomendaciones de la OMS sobre atención prenatal para una experiencia positiva del embarazo. Washington, D.C.: Organización Panamericana de la Salud; 2018. Licencia: CC BY-NC-SA 3.0 IGO.
  • Gómez, F. Núñez, and JL López-Prats Lucea. “Cardiopatías congénitas en niños con síndrome de Down.” Revista Española de 68.6 (2012): 415-420.
  • Tapia A. Estudio de coste-efectividad del cribado combinado del síndrome de Down en el primer trimestre de la gestación. Gestión y evaluación de costes sanitarios. Gestión y evaluación de costes sanitarios. Vol 12, monográfico 1. Enero-marzo 2011.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.