Fetal DNA test: what it is for, when to do it and how much it costs

The fetal DNA test is a non-invasive screening test that is used to evaluate the presence of any chromosomal abnormalities in the fetus, such as Down syndrome. Find out everything you need to know about this exam.

Fetal DNA testing or NIPT ( Non Invasive Prenatal Testing) is a non-invasive prenatal screening test  that allows you to calculate the probability that a child is affected by certain chromosomal abnormalities .

What information is possible with this test?

1. Abnormalities of chromosomes

Fetal DNA testing is mainly used to assess whether the unborn child is at low, medium or high risk for the following conditions:

• Down syndrome  or trisomy 21 (where trisomy is the presence of three 21 chromosomes instead of two)
• Edwards syndrome (trisomy 18) 
• Patau syndrome (trisomy 13) 
• Turner syndrome
• Klinefelter syndrome

However, it is important to underline that the fetal DNA test is not a diagnostic test (such as CVS or amniocentesis), but a screening test (such as the Bi-test). Therefore, it provides probabilistic and not certain data, even if, as we will see, it has a very high accuracy .

Extended DNA testing

At present, there is also the possibility of extending the study of fetal DNA to search for chromosomal anomalies linked to rarer syndromes , such as in the case of microdeletions (ie the loss of some small portions of DNA).

Currently, however, these extensions do not yet have the requirements to be validated and are therefore not recommended by Italian and international medical organizations .

At present, extended DNA testing should only be limited to couples who have knowledge of genetic disorders in their family and who refuse an invasive (100% diagnostic) test . The couple who do not want an invasive diagnosis can eventually start with this test and then decide on the other way.

2. Gender of the child

NIPT is able to establish with certainty whether you are expecting a boy or a girl , as it also analyzes the sex chromosomes.

3. Rh factor of the child

In the case of a mother with a Rh negative blood group , NIPT can also give information on the Rh factor of the fetus (i.e. whether it is positive or negative) with a sensitivity of 99.7% .

How is the exam done?

Compared to CVS and amniocentesis, this test has the advantage of being very simple to perform and absolutely safe for both mother and baby.

The test is conducted by isolating the fragments of fetal DNA that circulate in the mother’s blood during pregnancy. To carry out the analysis, therefore, it is sufficient to undergo a simple blood draw . Fasting before the test is not required.

The main scientific societies recommend performing the fetal DNA test in combination or after an accurate ultrasound for the evaluation of nuchal translucency. This ultrasound evaluation, in fact, has a very important value in the evaluation of fetal anomalies.

In some structures, moreover, the exam also includes an interview with the geneticist :

• before the exam, to explain the advantages and disadvantages and choose the best test for the single situation;
• upon delivery of the outcome, to communicate the results and evaluate the next steps to be taken based on the level of risk highlighted.

How long does it take to receive the test results?

The result of the exam is generally communicated after 1 or 2  weeks and in any case within 20 days at the latest. Today, however, tests are available that allow you to receive the result within 5 working days .

In the case of medium or high risk , the expectant mother will evaluate together with the gynecologist or geneticist whether to undergo further investigations, represented by invasive diagnostic tests such as CVS ( between 10 ^and  13  ^weeks  ), amniocentesis (between 16th ^and 18th ^week ) .

Fetal DNA testing: when to do it?

The test can be performed as early as the 10th ^week of pregnancy , but nothing prevents it from being performed later. Usually, however, it is recommended to do this by ^week 16 . At this gestational age, in fact, the woman will have the time to carry out further investigations, if necessary, and the possibility of evaluating a possible voluntary interruption of the pregnancy within the terms established by Italian law.

Can the fetal DNA test be wrong?

The fetal DNA test is highly reliable : in fact, clinical tests show that it is able to detect the presence of risk:

• in 99% of cases for Down syndrome
• in 97% for trisomy 18
• in 92% for trisomy 13 .

In addition, the rate of false positives (i.e. where the result is false positive) is very low and stands at:

• less than 0.1% for Down syndrome
• less than 0.5% for trisomy 18 and 13

On the other hand, since it is a screening exam, the fetal DNA test does not allow to establish with absolute certainty the presence or absence of genetic anomalies , but only to calculate the percentage of risk . Consequently, this analysis does not replace invasive tests such as CVS and amniocentesis. 

Furthermore, the test is not reliable in case of monochorionic pregnancy with more than two fetuses.

Finally, it should be remembered that in 4% of cases the circulating fetal DNA may not be sufficient to obtain a reliable result. In this case, however, the test can be repeated.

Fetal DNA testing: in which cases is it recommended?

Being risk-free, fetal DNA testing can be performed by any woman who wishes . However, there are some situations in which it is more recommended : 

• pregnancies in which invasive diagnosis is contraindicated (such as in the case of previous abortions or assisted reproduction )
• first trimester screening test (bi-test and nuchal translucency) with an intermediate/high risk outcome of chromosomal abnormalities
• women over the age of 35
• family history of genetic diseases

Fetal DNA test: costs (2021/2022)

Unfortunately, the cost of the test is very high and varies according to the structure chosen and the region of residence, starting from a figure of 300 Euros up to over 1,000 .

However, it should be noted that Emilia Romagna is the first Italian region to offer free fetal DNA testing to all resident women , regardless of age and the presence of risk factors, while the Tuscany region offers a reduced rate or the exemption for specific categories of women .

Other regions and autonomous provinces are introducing exemptions and subsidized costs for future mothers at risk , so the advice is to get information from your general practitioner or local health authority.

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Main sources

• Higher Institute of Health: “Fetal DNA test (investigation tests)”.
• Ministry of Health: “Non invasive prenatal screening guidelines based on DNA (Non Invasive Prenatal Testing – NIPT)”.
• National Health Service: the LEA.