NIPT (Fetal DNA Test): What Is It For, Who Is It Offered To and How Are Results Interpreted?

NIPT (fetal DNA test) is a screening test that estimates the likelihood of some chromosome anomalies by examining fragments of the baby's DNA circulating in the mother's blood; it does not make a diagnosis. A high-probability result does not show that there is an anomaly; a low-probability result does not completely rule out an anomaly either. To whom the test is offered varies by country: current recommendations in America say that this kind of screening can be offered regardless of age and initial risk level; in the United Kingdom, on the other hand, the test is offered, for further assessment, to pregnant women whose combined or quadruple test result shows a high probability. In Turkey, the planning of the test depends on the assessment of the doctor who follows you. Whether to have it or not is your decision.

What sample is taken for NIPT, and what is examined?

During pregnancy, cell-free DNA fragments, most of which come from the placenta, are found in the mother's blood. NIPT analyses these fragments in a blood sample taken from the mother. Because no intervention is needed other than taking a blood sample, the test is called "non-invasive".

Is NIPT a diagnostic test?

A screening test estimates the likelihood of a condition. A diagnostic test, on the other hand, is aimed at determining whether that condition really exists. NIPT falls into the first group. People whose result comes out as high probability are offered a diagnostic test option to confirm the result.

What does NIPT screen for, and what does it not screen for?

NIPT generally estimates the likelihood of Down syndrome (chromosome 21), Edwards syndrome (chromosome 18) and Patau syndrome (chromosome 13); it does not assess other chromosome conditions and single-gene diseases. In other countries and laboratories the scope may be different; which conditions are screened varies with the test, and the doctor and laboratory give information on this.

The test does not give a correct result in every case; false positive and, rarely, false negative results can be seen.

Is NIPT offered in the same way in every country?

Current recommendations in America state that cell-free DNA screening can be offered without looking at the person's age and initial risk level; they also emphasise that no single method is most suitable for all people. In the United Kingdom, on the other hand, the test is offered, for further assessment, to pregnant women whose combined or quadruple test result shows a high probability. The two approaches stand side by side; the doctor who follows the pregnancy assesses which suits your situation.

Is NIPT suitable in a multiple pregnancy or an IVF pregnancy?

Whether the test is suitable in a multiple pregnancy, or in pregnancies formed by IVF or with donor eggs, varies with the type of test and the institution at which it is done. In this matter the knowledge of the doctor who follows the pregnancy is the basis.

Who determines the NIPT plan in Turkey?

In Turkey, to whom, when and with which laboratory method the test will be recommended depends on the plan of the doctor who follows you.

What does a low-probability result mean?

A low probability shows that the likelihood of the conditions screened for was found to be low. It gives no information about the conditions not screened for; nor does it completely rule out the conditions screened for.

What is discussed when you receive a high-probability result?

A high-probability result is not a diagnosis. In this case you are offered a diagnostic test to confirm the result, or the option of not having an additional test. The doctor who will recommend the procedure discusses the details of the diagnostic test with you separately. It is useful to set aside time with your doctor to understand what the result means.

What is done if no NIPT result can be obtained?

Sometimes no analysable result comes out of the blood sample. In this case, one of the options of taking a second sample, doing a diagnostic test or not doing an additional test is discussed. Not obtaining a result is not a diagnosis on its own; you discuss with your doctor the reason and the next step (a second sample, additional assessment or a diagnostic test).

What is the difference between NIPT and the combined test?

The combined test calculates risk by combining a measurement done on ultrasound with the results in the mother's blood. NIPT, on the other hand, examines fragments of fetal DNA in the blood directly. The two methods rest on different information and are not presented in a way that could be compared with the same criteria; the doctor assesses which will be applied, or in which order, according to your history and preferences.

Is it compulsory to have the test?

No. Offering screening and diagnostic test options to all pregnant women also includes the person's right not to want one or both of them. Not having NIPT, or having it and then not wanting an additional test, are both valid options. Thinking beforehand about what you want to do with the result can make the decision easier.

How can you get support if your anxiety increases while waiting for the result?

Waiting for the result, or receiving a high-probability result, can create intense anxiety. You can ask your doctor to explain the result in an understandable way and, if necessary, bring up the option of genetic counselling. It is recommended that the conversation be person-centred, with you and your needs at the heart of it. If your distress makes daily life difficult, you can also get support from a mental health professional.

What information should you give your doctor when discussing the test?

• If there has been a chromosome condition in earlier pregnancies or in the family, say so at the start of the consultation.
• If the pregnancy was formed with IVF or donor eggs, mention this too.
• Ask what the NIPT option you have screens for and what it does not.
• Clarify by whom, by what route and when the result will be communicated.
• Ask before the result what can be discussed if it comes out as high probability.