Explaining several types of prenatal screening tests
A combined test screens the baby for Down's; Edwards' and Patau syndrome
Down's syndrome is the most common genetic disorder. Your age affects the risk of Down syndrome in your baby. At 25, the risk is about 1 in 1400. At 35 this has become 1 in 350. By using a combination of different risk factors, a more accurate risk assessment can be made. A risk assessment for having a child with Patau’s and Edward’s syndrome is made as well. These are serious conditions including brain and physical abnormalities and a very limited life expectancy.
Highest risk factors are maternal age, nuchal translucency thickness and protein level in the mother’s blood. To determine this level, a blood test is done at 10 weeks of pregnancy. The nuchal translucency (NT) scan is performed at around 12 weeks of pregnancy.
The thinner the nuchal translucency measurement the better. You will be offered further testing at a nuchal thickness of over 3.5mm; this could indicate your baby has a heart defect. If the screening test shows a result higher than 1:200, you will be offered further testing as well. Extra tests will include a NIPT-test, chorionic villus sampling (CVS) or amniocentesis.
The combined test isn’t covered by your basic insurance policy and will cost around €175.-
The combined test is completely safe for you and your baby and does not cause a miscarriage. Because a NIPT-test is now available as well, combined testing isn’t performed much anymore. For most pregnant women, the NIPT will offer a more accurate result.
NIPT screens your baby for Down's syndrome, Edwards' syndrome and Patau's syndrome
Non-Invasive Prenatal Testing (NIPT) screens your baby for Down's syndrome, Edwards' syndrome and Patau's syndrome (trisomy 21, 13 and 18). A sample of the mother’s blood is taken from her arm which is used to look at DNA from your baby's placenta. The NIPT usually provides a more reliable result than the combined test. A low-risk result is very accurate (99.9%), however, a result showing a possible chromosomal abnormality is less accurate. In that case more testing needs to be done via chorionic villus sampling or amniocentesis.
Even though the government will cover most of the costs for the test - because of research purposes – you will have to contribute some of it yourself: €175.-. This is the amount that is not covered by your health insurance. The NIPT is completely safe for you and your baby and does not cause a miscarriage.
At the 20-week scan your baby is examined from head to toe
The 20-week scan aims to identify any possible structural (anatomical) anomalies; the baby is examined from head to toe. It also measures your baby’s growth, checks the amount of amniotic fluid and the position of the placenta. The sonographer can also tell you whether you’re expecting a boy or a girl.
The 20-week scan is performd at VCO scancentre. In case an anomaly is suspected, you will be offered further testing. We will refer you to our colleagues at the OLVG or the AMC.
A 20-week scan is performed anywhere between 19 and 21 weeks and will be completely covered by your basic health insurance.
Chorionic villus sampling or amniocentesis involves removing and testing a small sample of cells from the unborn baby
Sometimes you qualify for this type of invasive testing directly:
You have given birth to a child with a rare disease before
Someone in your direct family has given birth to a child with a rare disease
Your combined test showed a higher-chance result or the NIPT result was abnormal.
The 20-week scan showed reasons to suspect anomalies.
During chorionic villus sampling (CVS) (between the 11th and 14th weeks of pregnancy),
a small sample of cells is removed from the placenta. During amniocentesis (from 15 weeks of pregnancy) a small sample of amniotic fluid is removed for analysis.
First, a quick screening is done for the most common chromosomal abnormalities; the results should be back after about 5 working days. If necessary, more extensive screening will be done for more chromosomal abnormalities. These results should be back after about 3 weeks. Both tests carry a small risk of a miscarriage of about 3 to 5 out of every 1000 women.