Prenatal screening – The combined test

In 2007 the authorities issued a permit to examine (screen) babies prenatally for chromosomal disorders or the presence of congenital defects. 

Why screening is necessary

Most babies by far are healthy. Some, however, are born ill or they may have a disorder. It is why women are offered a number of screening sessions during and shortly after pregnancy, to find out whether any illness or disorder might exist. Obstetricians will bear this in mind during delivery. Doctors can start treatment at an early stage, and parents are informed on time about their child’s health, so they can decide on the steps they wish to take. 

First trimester

In the first three months of pregnancy you can find out whether your child is likely to develop the Down, Edwards or Patau syndrome. (Trisomy 21, 18 and 13).

During the combined test, the ultrasound operator will study both the thickness of the skin fold behind the nape of the neck and whether two critical hormones exist in the mother’s blood.


We prefer to perform the combined test in two stages: 

  1. Your first visit will be between 9 and 11 weeks of pregnancy. You will have an ultrasound to determine the pregnancy period and we will take some blood to find out whether the two hormones are present.

  2. Your second visit will take place between 11+5 and 13+5 weeks of pregnancy. During this visit we will ultrasound measure the thickness of the skin fold behind your child’s nape of the neck. We will show you the results directly afterwards.

The combined test results are shown in a risk. In case of a higher risk you can choose to have a follow-up test to be reassured. 

If you need more information about this test you may contact your obstetrician or consult the RIVM leaflet.

Folder informatie over de screening op down edwards en patausyndroom Engels    Download here the RIVM leaflet on screening for Down syndrome.



A negative ultrasound and/or screening outcome usually means a troubled pregnancy. To diagnose matters properly, a follow-up test in recommended in most cases. The follow-up test involves a so-called corionic villus sampling (between 11 and 14 weeks of pregnancy) or an amniocentesis (after 15 weeks of pregnancy). Sometimes a detailed ultrasound is performed. This follow-up test is also referred to as the prenatal examination. Depending on the nature and seriousness of the abnormality at hand, this test will be performed in the second or third line (at the regional or academic hospital).

The ultrasound operator will answer all your questions about the results and schedule a follow-up test (if necessary) or an appointment with your obstetrician and/or gynaecologist.