Prenatal Screening

Prenatal screening allows us to gain insight into the chance that your baby has certain defects. The greater the maternal age, the greater the chance of these defects. At the first appointment we will give you extensive information, and we will answer your questions. It can be a difficult decision whether or not to have prenatal screening, and therefore we recommend you read something about the screening in advance.

The Combined Test

The combined test is a screening test for Down syndrome (trisomy 21). The chances of a baby with Down syndrome increase as the age of the mother increases. The combined test gives an estimation of the risk, based on the specific characteristics of your pregnancy. Reliability of this test is about 85%.

If you participate in a screening, it is also possible to get additional test results of other chromosomal abnormalities: trisomy 13 and 18. Both disorders are chromosomal defects that cause severe physical and mental disabilities.

The combined test does not carry any risks for mother or child, but the results may urge you to make a choice whether or not you want to have further tests (amniocentesis or chorionic villus sampling). If you are under 36, the combined test will not be covered by your insurance. In 2011, a combined test cost €149.

Age of the mother	Chances of a child with Down syndrome
20 - 25 year	1 in 1.000
26 - 30 year	1 to 2 in 1.000
31 - 35 year	2 to 5 in 1.000
36 - 40 year	6 to 15 in 1.000
41 - 45 year	20 to 61 in 1.000

The combined test consists of two different tests:

Early serum screening. This is a blood test for the mother, which tests for 2 substances (PAPP-A and free beta HCG). The levels found in this test are compared against the mother’s age, weight, and whether she smokes or not. This test is carried out between 8 and 14 weeks of pregnancy.

Nuchal translucency measurement (or NT-scan) measures the amount of fluid accumulation that can be seen behind the neck of the 11 to 13 weeks old baby. Abnormal levels in the blood test or a larger neck fold might indicate a greater risk of a child with Down syndrome.

By combining the results of both tests, a personalised risk assessment can be made. Based on the results of these tests we can find out whether you are at high or at low risk of having a baby with Down syndrome.

High risk

There is an increased risk if your chances of having a child with Down syndrome are 1 in 200 or higher. To help determine whether the foetus indeed has Down syndrome, further tests are necessary. These tests include:

Either amniocentesis at 16 or 17 weeks of pregnancy, or chorionic villus sampling (CVS) at 11 to 13 weeks of pregnancy.

Both CVS and amniocentesis procedures carry a slight risk of miscarriage. These risks are 1 in 200 for CVS and 1 in 300 for amniocentesis.

Risk assessment

Based on the information that you give us during the first appointment, we will perform a risk assessment. If you seem at high risk of having a baby with birth defects, we will discuss several possible examinations with you. You might have an increased risk if you are older than 36 (in the 18^th week of pregnancy), or if there are (genetic) abnormalities in a previous child, or in one of the parents’ families. If yours appears to be a high-risk pregnancy, we will also discuss with you which tests may be performed to further determine how high the risk is.

Further information

Via the links in the top left corner of this page, you can find further information about prenatal screening. This information also goes further into detail of what Down syndrome really is. Furthermore, there is a decision aid to help you choose whether or not to have prenatal screening.

The 20-weeks’ ultrasound

Between 18 and 22 weeks of pregnancy you may choose to have a second trimester ultrasound. This ultrasound will show any visible physical abnormalities in your baby. A specially trained sonographer will perform this examination with an advanced ultrasound machine. Your insurance company will reimburse this second trimester ultrasound.