Prenatal screening

Prenatal screening is defined as tests that say something about chromosomal abnormalities in the unborn child. The most frequent chromosomal abnormality is Down's syndrome in which a child has three chromosomes 21 instead of two; trisomy 21. A child generally can have a good live with this syndrome. A child with Down's syndrome usually has mental retardation and frequent medical problems like heart defects, intestinal problems and hearing problems. There are two other trisomies which presently can be tested: trisomy 18 (Patau's syndrome) and trisomy 18 (Edward's syndrome). These two are less common because it is much harder for children to develop and live with these trisomies. Many pregnancies with children who have trisomy 13 or 18 end in a miscarriage or stillbirth. Occasionally these children will be born alive, but usually suffer from multiple defects and problems which cause a short-lived life. Children who live weeks, months or even a couple of years are an exception. The chance of a child with a chromosomal abnormality increases with the age of the mother (see a table with the chances printed below on this page).

At this moment, pregnant women can choose between two tests if they want information about the chance of having a baby with a chromosomal defect: the NIPT (Non Invasive Prenatal Test) or the combination test.
If pregnant women want to have information about possible physical abnormalities they can make an ultrasound around 20 weeks pregnancy.

The NIPT and the combination test give odds of having a child with a chromosomal problem as a result. The NIPT gives a more accurate result than the combination test.
The 20 week ultrasound looks for physical abnormalities.

In the beginning of your pregnancy we will give you information about the different tests if you want to.

The NIPT:

At this moment two studies are being conducted in the Netherlands to evaluate the NIPT: the TRIDENT-1 and the TRIDENT-2 study.
Almost all pregnant women can choose for the NIPT in the TRIDENT-2 study and women with an increased chance after the combination test (see below) qualify for the TRIDENT-1 study.
The NIPT is a test that uses the mother's blood to check the baby for Down, Edwards or Patau syndrome. The test is not 100% accurate, but if there is a normal outcome further testing is not necessary (because then the chance that there is an abnormality with chromosomes 13, 18 or 21 is less than 1:1000). If the test says that there is evidence for an abnormality, further tests are offered (chorionic villus sampling or a amniotic fluid test). These tests give a small miscarriage risk (1:500) but they do give 100% certainty about Down, Edwards or Patau Syndrome.

What to do if you want the NIPT:
First of all visit the following websites: www.onderzoekvanmijnongeborenkind.nl and www.meerovernipt.nl.
Plan an ultrasound around 11 weeks of pregnancy. Max one week is allowed between the ultrasound and the taking of the bloodsample for the NIPT so take that in consideration in your planning.
The blood for the NIPT can be taken from 11 weeks gestation.
Send an e-mail to our assistant. State in that e-mail that you want to collect a lab form for the NIPT, whether or not you want to know additional findings and if you give permission for saving and using left over material (see: consent form NIPT). Collecting a lab form is possible from exactely 11 weeks gestation.
Collect your lab form and sign the consent form at our practice.
Now first pay for the NIPT: www.niptbetalen.nl. You need the number in the top left corner of the lab form to pay. You will receive a receipt in your e-mail.
With the lab form and your receipt (on your phone or printed) you can go to a laboratory where they can draw blood for NIPT, for example at our ultrasound center.  
When the results are in (about 10 working days) and the results are normal, you will receive an e-mail from us. In all other cases you will receive a phone call.

The NIPT costs 175 euro.

The combination test:

This test combines a blood test with the thickness of the nuchal fold (in the neck of the baby) which is measured during an ultrasound at 12 weeks pregnancy. This tests gives odds as a result (a probability scale), and not a definitive result.

The combination test costs 168 euro.

When given odds you will get a result of (for example) 1:2000, 1:500 or 1:30. 
A chance of 1:200 or higher (i.e. 1:100, 1:50) is seen an increased chance of having chromosomal abnormalities. With an increased chance you are given the option to do the NIPT (in the TRIDENT-1 study) or chorionic villus sampling or a amniotic fluid test. With a chance of 1:200 or lower further additional testing will not be offered.

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This illustrations show a chance of 1:200 (one in two hundred). 
One out of two hundred pregnant women will have a child with a chromosomal abnormality.

In the end the only way to be 100% sure about the presence of an chromosomal abnormality is to do chorionic villus sampling or an amniotic fluid test. This additional test will always be reimbursed when someone has an abnormal NIPT of an increased chance from the combination test.

The 20 week ultrasound:

Every woman has the opportunity to have an extensive ultrasound around week 20 of the pregnancy. It is a complete check for physical abnormalities with the baby. The size of the baby is also measured.
This ultrasound will be reimbursed by the basic package of the health insurance company. 

The idea behind this ultrasound is that it gives the parents a choice. If a (serious) defect is found, the pregnancy may be terminated until week 24 of the pregnancy. With certain defects it may be beneficial to know that the child has need of a particular treatment or care. The disadvantage of this ultrasounds is that frequently something abnormal is found that, in retrospect, was not an indication of a defect. Or that something abnormal is found that doctors cannot give any information on because they cannot determine what precisely has been found so nothing can be clarified. Such an outcome can cause (mostly temporarily) stress and doubt to the parents. This can "ruin" the remainder of the pregnancy which can be very stressful. Especially if it turns out be nothing to worry about. 

To choose: 

The goal of the NIPT and the combination test is to detect chromosomal abnormalities. Such deviations cannot be cured. For example, if a child is diagnosed with Down's syndrome, the parents to be must make a choice. They can accept the fact that they will have a child with this disorder or they can choose to terminate the pregnancy. The question that parents to be must ask themselves is what they would do with the result of a test. How important do they feel it is to have a choice? Or, how important do they feel it is to not have to make that choice? 

All pregnant women have the choice to be tested or not. On the RIVM (Rijksinstituut voor Volksgezondheid en Milieu) website there is a decision support 'bewust kiezen' (choose consciously) to help.

From the previous one can gather that there are different sides to prenatal screening. The balance of pros and cons will be different for each person. A lot of pregnant women want to hear that all is and will be well with their child. It is important to realize that the health of a child can never be guaranteed even if all screening has been done.
Furthermore it is important to consider how the likelihood of having a child with chromosomal abnormalities really is. When thinking about deviations it is easy to forget that the vast majority of children are born completely healthy. The limit for a test result is with a chance of 1 in 200. You can roughly state that for women that are younger than 36 years the chance will be below that 1 in 200; less than a half percent. When reaching 36 years of age that chance is about 1 in 200 and increases with age to about 1 in 100 when one reaches 40 years of age; about 1 percent.

Questions a pregnant woman can ask herself and her partner (if she has one) are:

- How do I feel about a child with a chromosomal abnormality in my family?

- What do I  think about the risk of having a miscarriage when she would choose to do chorionic villus sampling or a amniotic fluid test.

- Would I terminate the pregnancy if I found out my baby had a defect?

- What do I feel constitutes an increased chance and what chance is acceptable to me? 

That the answers to those questions are different for everyone is obvious. That is the reason it is not possible to give advice in these matters. Each pregnant woman must, together with her partner, make decisions in these matters because she must live with those decisions and the consequences of them.  

If there are defects or diseases to be found in your family or if you have a defect or a disease yourself and you think your child can get this too please try to inform yourself about this (preferably before a pregnancy) as soon as possible. You can call us for information or you can call the ERFO telephone number of the VSOP (Joined parents and patients organizations for hereditary or congenital defects) at 035 6034040.

Age of the mother at the time of the test        Chance of having a child with Down's syndrome

20-25 years of age                                                11 to 13 out of 10,000

26-30 years of age                                                14 to 19 out of 10,000

31-35 years of age                                                20 to 45 out of 10,000

36-40 years of age                                                60 to 155 out of 10,000

41-45 years of age                                                200 to 615 out of 10,000

Additional information:

www.onderzoekvanmijnongeborenkind.nl
decision support: choose consciously
NIPT: 2 studies
Kiesbeter.nl
Echo Amsterdam: laboratory for NIPT
www.prenatalescreening.nl
erfocentrum
Help by making a decision when there is a hereditary disorder in the family
chorionic villus sampling
amniotic fluid test
hoeverder.info: If an abnormality is found you will find independent information here about whether or not to continue with a wanted pregnancy