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Prenatal screening

Prenatal screening

Screening | Diagnostic tests | CVS chorionvillisampling | Amniocentesis | NIPT

Choosing a Test
A screening test looks for pointers for certain conditions and assesses your risk against the average risk of having a baby with certain abnormalities. A ‘positive” screening test does NOT mean that the baby has an abnormality. In fact chances are very much in favour that the baby is perfectly fine. But the result means that a further test is offered to you-a diagnostic test.

All pregnant women can have a screeningstest done, no matter your age or health. But the Insurance will only pay the combinationtest if you have a higher risk on account of heriditary diseases in the family.

When you visit us the first time we will tell you about the possibilities to perform screening and diagnostic tests. The screening and diagnostic tests will give you an idea of how your baby is developing, and which can pick up possible problems.

The anomaly scan is covered by the insurance.

There are two forms of screening offered: 
- The combinationtest: This is a screeningtest for Down’s syndrome, Patau syndrome and Edwards syndrome

The test is a combination of two tests:
A bloodtest between 9 and 13 weeks pregnancy. Looking for 2 proteins in your blood. An increased or decreased level of the proteins can be a pointer of Downs syndrome.
An ultrasound between 11 and 14 weeks pregnancy, where the nuchal fold will be measured. The nuchal fold is a layer of fluid at back of the neck of the baby. The thicker the layer is, the greater the chance of having a baby with Downs syndrome. The combinationtest will be performed in centrum SAM&.
The combinationtest is in most cases not covered by your insurance company, so we advice you to check your insurance in advance. On the website centrum SAM& you can find the price (around 160 euro in 2016).

- The anomaly scan: (20 weeks ultrasound).
The anomaly scan is an ultrasound performed around 20 weeks of you pregnancy to screen on a number of fetal abnormalities such as spina bifida, cleft palate or heart defects. This scan will also take place in centrum SAM&
Both screeningstests cannot give you a definitive answer whether your baby has a specific abnormality, but will give you an assesment of the risk for your child. If you have an increased risk you will be offered a diagnostic test.

If you have an increased risk on Down’s syndrome after doing a screening test you will be offered a NIPT test.

NIPT is a new test, which is available since April 1 2014, as a pilot in the Netherlands TRIDENT study. The NIPT (Non Invasive Prenatal Test) is a test in which maternal blood is used to test whether the unborn child may have trisomy 21 (Down syndrome), trisomy 18 (Edward 's syndrome) or trisomy 13 (patausyndroom).

NIPT is offered to women with an increased risk of having a child with a trisomy after the first trimester screeningtest

NIPT is a test, in which blood is taken from the pregnant woman and examined in a laboratory. In the blood of the mother is DNA (genetic material) of the child present. With the NIPT test this DNA of the child can be tested for trisomy 21 (Down syndrome), trisomy 18 (Edward 's syndrome) and trisomy 13 (patausyndroom). The NIPT does not provide 100% guarantee. International research shows that the test in pregnant women with an increased risk of the following can detect more than 99 of the 100 (99%) unborn children with trisomy 21;

97 out of 100 (97%) unborn children with trisomy 18;

92 out of 100 (92%) unborn children with trisomy 13.

If you receive an abnormal result of the NIPT there are strong indications that the unborn child has a trisomy 21, 18 or 13. However, to know for sure you will be offered to do an amnioncentesis or CVB.

Most of the results are not abnormal. In a non-abnormal result,  the probability that the child still has a trisomy is so small (less than 1 in 1000) that an amniocentesis or CVB will not be offered.

At about 3 in 100 women the NIPT fails to give a result.

Diagnostic tests
These test can give you a definitive answer about whether your baby has a specific abnormality

The test will be offered to you after an increased risk on Down syndrome after the NIPT test or if your child has an increased risk of certain diseases, which could be detected after an amniocentesis.

These diagnostic tests are only offered in case of a high risk result from the combinationtest or certain heriditary diseases in your family.

CVS chorionvillussampling
- Around 12 weeks of pregnancy a sample of placental tissue can be removed through the abdomen or the trough the vagina with a needle. The sample will be tested on chromosomal problems, such as down syndrome. The CVS is a reliable test. The risk of having a miscarriage due to the CVS is 0,5% (1 in 200).

- With an amniocentesis you can determine whether your child has serious chromosomal disorders, such as down syndrome, or a spina bifida. Around twelve weeks of pregnancy the obstetrician will then insert a needle through your abdomen and into the uterus to draw a small amount of amniotic fluid. This contains cells from the baby which can give a definitive answer about the chromosomes. Amniocentesis is also a reliable test. Unfortunately it also has a risk of having a miscarriage due to the test. This risk is smaller than with a CVS. The risk for Amniocentesis is between 0,3% and 0,5%.
The CVS and the Amniocentesis will be performed in an academic hospital, such as the VUmc.

Choosing a Test
You need to realize that with the screening and diagnostic tests you’ll be able to track a couple of disorders but not all of them, so the test will not guarantee a healthy child. The disorders which we are able to diagnose cannot be cured. Before choosing for a screening or diagnostic test it can be usefull to consider a couple of questions.

- How would you feel if you give birth to a child with congenital abnormalities. How would this affect your family?
- What would you do if your child has Downs syndrome or another abnormality, would you choose to terminate the pregnancy or would you just like to be prepared.
- If you don’t want to terminate the pregnancy, how do you feel about the risks of a miscarriage due to diagnostic test?
- About the combinationtest: what would be a low risk for you? Do you think that 1 in 200 is a good result, or would the limit be for instance around 1 in 50?

Making decisions about doing a screening or diagnostic test is always difficult. You are the only ones who can decide what the best decision will be for you and your family. When you visit us the first time you will have the possibility to ask questions, and be referred if you want to do the tests.