Prenatal screening

Prenatale screening

The majority of pregnancies are problem-free. Fortunately, most children come into the world in perfect health. Screenings during pregnancy and shortly after birth can identify any complications, diseases or disorders at an early stage, whereupon treatment can be offered. During pregnancy, you can have screening tests to find out whether your unborn baby has a congenital disorder or any physical abnormalities. This is called prenatal screening.

There are two screening tests:

  1. first trimester prenatal screening for Down syndrome, Edwards’ syndrome and Patau’s syndrome, and
  2. second trimester screening for physical abnormalities (anomaly scan).

It’s entirely up to you to decide whether or not you want to take these screening tests.


The NIPT (Non Invasive Prenatal Test) is a screening test in which the mother’s blood is used to assess in the laboratory whether there is evidence of Down syndrome, Edwards syndrome or Patau syndrome in the baby. The NIPT is only offered in the Netherlands in the context of two scientific studies: the TRIDENT-1 (for high-risk pregnant women) and TRIDENT-2 (for all pregnant women).

When you are pregnant, your blood also contains a small amount of hereditary material (DNA) from the placenta (placenta). This DNA is almost always the same as that of the child. This allows the laboratory to determine whether the baby has Down, Edwards or Patau syndrome. In addition, the NIPT can also provide indications of other chromosome abnormalities in the child, in the placenta (placenta) and very occasionally in the pregnant woman herself. These are so-called incidental findings. The abnormalities vary from very serious to less serious. You can indicate to the NIPT whether you also want to know these additional findings or not. More information about incidental findings can be found via this link.

Combined screening test

The combined screening test is a test for Down, Edwards and Patau syndrome. This is investigated on the basis of a blood test on the mother and an ultrasound in which the nuchal fold of the baby is measured. The blood test determines the concentrations of two hormones that the placenta produces. The height of these hormones, along with the thickness of the nuchal fold, the gestational age and the age of the mother, predict whether there is an increased risk.

The combination test is only performed at the Amsterdam UMC location VUmc.

Second trimester anomaly scan

The anomaly scan is a medical examination. Another name for it is the structural ultrasound scan. The aim is to find out whether the baby has any physical abnormalities. These include spina bifida (an open spine), anencephaly (where most of the brain and spinal cord is missing), hydrocephalus (water on the brain), heart defects, diaphragmatic hernia, abdominal hernia, either absent or abnormal kidneys, abnormal bone development, and abnormalities of the arms or legs. The sonographer also checks whether the baby is growing properly and whether there is sufficient amniotic fluid.

You can have an anomaly scan from week 18 to week 21 of your pregnancy (which is 21 weeks and 0 days into your pregnancy). It should ideally be in week 19 of your pregnancy (which is 19 weeks and 0 days to 19 weeks and 6 days into your pregnancy).
You can download  leaflets about the anomaly scan in five languages.

If any signs have come up during the anomaly scan, you will be referred to the Amsterdam UMC for further research (i.e. extended scans). 


How is first trimester prenatal screening performed?

After 11 weeks a blood test will be performed by the mother and analyzed by the lab of the Amsterdam UMC.

When can prenatal screening be performed?

NIPT: between 11 and 18 weeks pregnancy (at the lab at Echo Amsterdam)

Combined screening test: the bloodtest can be performed between 9 and 14 weeks pregnancy; the nuchal translucency measurement will be performed between 11 and 14 weeks  (in the Amsterdam UMC location Vumc)

SEO (second trimester anomaly scan): between 19 and 21 weeks pregnancy

What's the difference between NIPT and the combined screening test?

Studies have shown that the NIPT detects more cases of Down syndrome, Edwards’ syndrome and Patau’s syndrome than the combined test, and that it is often more accurate. This means that fewer pregnant women are unnecessarily referred for follow-up diagnostic testing.

What are secondary findings?

As part of the TRIDENT study, pregnant women can indicate whether they would like to be informed about any other chromosomal abnormalities in addition to trisomy 21, 18 and 13. In the context of a screening programme for trisomy 21, 18 and 13 these abnormalities are deemed to be ‘additional findings’. Of the pregnant women who chose to be informed about additional findings, 0.36% were identified as having a high-risk for chromosomal abnormalities other than the common trisomies. If you indicate you want to be informed about any additional findings, only those additional findings will be reported that (1) are known to cause or likely to cause disease, and (2) have severe consequences for the health of the baby if the finding were to be confirmed by diagnostic testing.

What are the costs?

Not all prenatal screening is covered by insurance:

NIPT: €175,-

Combinatietest: €176,96

Structureel echoscopisch onderzoek (second trimester anomaly scan): Covered by your insurancer. If you don’t have an insurance, it will cost €164,92

How to apply for prenatal screening?

The NIPT and Anomaly scan can be performed at our ultrasound center. The combined screening test is done exclusively at Amsterdam UMC location VUmc.

Click here to apply for the NIPT.

How reliable is prenatal screening?

The NIPT will detect:

  • 97 of 100 children with trisomy 21
  • 90 of 100 children with trisomy 18
  • 90 of 100 children with trisomy 13


The combined screening test detects:

  • 85 of 100 children with trisomy 21
  • 77 of 100 children with trisomy 18
  • 65 of 100 children with trisomy 13


The anomaly scan can detect numerous physical defects, however not all defects can be found.

What diagnostic tests are possible?

If the result of the NIPT, combination test shows abnormalities, you will be offered a follow-up examination. This follow-up examination consists of a villus test or an amniocentesis and takes place at the Amsterdam UMC (location VUmc or AMC). These tests determine with certainty whether or not the baby has abnormalities. These tests are invasive, meaning there is a small chance of miscarriage. The chance that this happened with the amniocentesis and villi test is about 1: 500 or 0.2%.

When will I receive the results?

NIPT: Within 12 days

Combined screening test: within a week after the scan if the blood test has been perform a week beforehand.

Anomaly scan: During the scan, the ultrasound expert will explain if she she’s (signs of) an abnormality and will suggest what fruitier research is necessary.

I'm pregnant with twins, can I still perform a NIPT?

Yes, if you are pregnant with twins you can opt for the NIPT non-invasive prenatal test. The result of the NIPT is just as reliable for identical twins as for a singleton. In fraternal twins, the NIPT may be slightly less reliable. Has NIPT found an indication of an abnormality? In that case, it is not known for fraternal twins to which child this result applies. This requires a follow-up examination of both children.