Blood test for Down, Edwards and Patau syndrome (NIPT)

Prenatal testing is always voluntary. In other words, all pregnant women can turn down any examination or test offered at any time without giving a reason. The right to not know is so important that nobody can force you to do prenatal testing.

Prenatal testing can have far-reaching consequences. Before deciding whether to have NIPT to look for Down syndrome, Edwards syndrome and Patau syndrome, it's important to think about the following questions and seek good advice early enough:

• Do you even want to know if your unborn baby has one of these trisomy syndromes?
• What would you do if the test results showed it was likely? Would you still definitely want to have the baby? Or would you consider terminating the pregnancy?
• What do you know about children with a trisomy syndrome?
• Do you need more information?

NIPT examines the child’s DNA (genes) that is shed by the placenta. This DNA – known as cell-free DNA – is found in the mother's bloodstream. The test is called “non-invasive” because doctors don't need to access the womb to get the sample. NIPT does not increase the risk of miscarriage.

The test involves taking blood from a vein in the mother’s arm. From around the 10th week of pregnancy onwards, her blood contains enough of the unborn baby’s DNA for it to be examined in a laboratory. The test results usually come back within a week. The doctor will share the results with you at an appointment.

It is also possible to agree in advance to only be told certain NIPT results – like only the Edwards and Patau syndrome results but not the Down syndrome result.

As of July 2022, statutory health insurers now cover the costs of NIPT to look for Down, Edwards and Patau syndrome (trisomy 21, 18 and 13) in certain situations. This test is not a part of routine screening in pregnancy. The costs are covered

• if other tests or examinations have found signs of a trisomy syndrome, or
• if a woman and her doctor believe and agree that the test is necessary in her personal situation.

For instance, the woman may be so distressed by the possibility of her child having one of these syndromes that she wants to have it checked.

Signs of a trisomy syndrome may be found during normal check-ups and the first trimester screening that some gynecologists offer between the 12th and 14th week of pregnancy. The first trimester screening involves an ultrasound scan and measuring certain things in the pregnant woman's blood. That can show signs of trisomy syndromes and other abnormalities. But first trimester screening can only say whether it's likely, and can't tell for sure. In Germany, the costs of first trimester screening usually aren't covered by statutory health insurance. It costs between 150 and 250 euros.

Your doctor will tell you the results of the test and talk to you about what they mean. The following three results are possible:

The only way to be sure that abnormal NIPT test results are accurate is by doing a procedure to analyze the baby’s DNA. There are two options:

• Taking a tissue sample from the placenta (chorionic villus sampling): possible from the 12th week of pregnancy onwards. The tissue is analyzed in a laboratory. Preliminary results are available after about two days, and it takes about two to three weeks to get the final results.
• Taking a sample of amniotic fluid from inside the womb (amniocentesis): possible from the 16th week onwards. The results are available after about two weeks. There is also a fast test that gives you the results after one to two days. But you will usually have to pay for it yourself. In both of these examinations, the doctor inserts a thin needle into the womb through the wall of the belly. An ultrasound scan is done at the same time so they can see where the needle is. You don't usually need an anesthetic.

The procedure itself isn't very painful. You might have a slight cramping feeling in your lower belly for a few hours or days afterwards.

Miscarriage is a more serious possible side effect. About 1 to 4 out of 1,000 women lose their baby as a result of the procedure. For this reason, doctors try to avoid doing chorionic villus sampling and amniocentesis if possible.

NIPT tests are generally accurate, but in rare cases the results are wrong ("false"). Because of this, trisomy syndromes can't be diagnosed for sure based on NIPT alone. One of the above procedures is needed in order to be certain.

NIPT can lead to two errors:

• The unborn baby has a trisomy syndrome but the test fails to detect it. When it comes to Down syndrome, that happens in less than 1 out of 10,000 examinations.
• The test results are abnormal, suggesting that the unborn baby has a trisomy syndrome, but that isn't actually the case. This is known as a “false positive” result. Regarding Down syndrome, that happens in about 5 out of 10,000 examinations.

These kinds of errors are more common with Edwards and Patau syndrome than with Down syndrome.

The chances of test results being correct will depend on the likelihood of a baby having a trisomy syndrome. That likelihood is influenced by a number of things, including the mother's age.

Let us assume that 10 out of 10,000 pregnant women have an unborn child with Down syndrome. If the NIPT tests of all of those women do not fail to provide results, this is what happens:

In other words: One third of all the abnormal results in this example are "false alarms" (5 out of 15 women).

This example shows that

• the vast majority of women have normal NIPT results (a low risk of having a baby with a trisomy syndrome).
• even if the NIPT test results are abnormal, it doesn't mean that the unborn baby actually has a trisomy syndrome. It can also be an incorrect finding (a false positive result).
• abnormal NIPT results have to be confirmed by doing a further examination, such as amniocentesis or chorionic villus sampling.

If an unborn baby is shown to actually have a trisomy syndrome, some women and couples ask themselves whether they want to carry on with the pregnancy or terminate it. They often feel pressured to make a decision before the 12th week. But there is no time pressure here: The pregnancy can also be terminated after the 12th week. So there's enough time to seek professional advice, talk to your family and friends about it, and make a decision.

It may also be helpful to meet up with children or adults with Down syndrome, or talk with their parents. You can ask your doctor for the addresses of support groups that will put you in contact with people who are happy to talk to you.

Many children with Edwards syndrome and Patau syndrome only live for a short time after birth. But some women and couples still want their baby to be born. They don't want to “decide” when the child passes away. Families who go through this kind of birth are offered special medical and psychological support, known as “perinatal palliative care.” This gives parents the chance to get to know their child and say goodbye to them.

This article can't provide answers to all questions about non-invasive prenatal testing for trisomy syndromes. It is intended to help you during appointments with your doctor or other professionals.

The German Federal Centre for Health Education (BZgA) has a search function for local pregnancy advice centers (Schwangerschaftsberatungsstellen) in Germany.

Information about trisomy syndromes can be found on many sites, including:

• www.cdc.gov: General information about Down Syndrome on the website of the Centers for Disease Control and Prevention
• www.leona-ev.de: Arbeitskreis Down-Syndrom Deutschland e. V. Germany-based support group for families with rare chromosome mutations (such as Edwards syndrome and Patau syndrome)