Prenatal screening
Every expectant mother in the Netherlands, regardless of age and medical background, has the possibility to determine the risk of having a child with a (serious or not) ailment. The current options are:
Since April 1st, 2017, the NIPT (non-invasive prenatal test) has been part of the prenatal screening options in the Netherlands.
As part of the NIPT, some blood is drawn from the expectant mother, after 11 weeks of pregnancy. This blood is tested in a laboratory to see if the fetus has any evidence of Down, Edwards or Patau syndrome.
The blood contains circulating free DNA (cfDNA). A small portion of this (about 10%) originates from the placenta, the vast majority (90%) originates from the expectant mother. These free DNA fragments are examined during the NIPT. If a relatively large number of DNA fragments from chromosome 21, 18 or 13 are found in this blood, this is an indication of the presence of Down, Edwards or Patau syndrome, respectively, in the fetus.
In addition to the above, clues to other syndromes may be found coincidentally. These are called secondary findings. Please note that checking for these syndromes is not part of the standard procedure. Upon requesting the NIPT, you need to choose whether or not you wish to be notified about these secondary findings. In the Netherlands, the NIPT does not look at the baby’s gender.
The test results are available after approximately 10 working days and will be provided to you by the midwife. When the results are not abnormal, no follow-up testing is necessary. When they are abnormal, there is a chance that the fetus has a syndrome. You can have follow-up diagnostic testing to make sure.
In case of secondary findings (and when you would like to be notified), someone will call you and explain what has been found and what this may mean for you or your child. You will receive an invitation for a counseling session at a university medical centre’s clinical genetics outpatient clinic where you will be given more information about the abnormality that has been found. Follow-up diagnostic testing is always necessary, just to be sure.
In case no secondary findings are reported, you will be notified of the same. No follow-up diagnostic testing will be needed. But please note: NIPT does not detect every possible type of chromosomal abnormality. There is still a small chance that your baby may have a disorder.
You may not be eligible for the NIPT if at least one of the following criteria are met:
- The fetus was already diagnosed with an abnormality (e.g. a nuchal fold thickness ≥ 3.5 mm).
- The expectant mother (or father) has a chromosomal abnormality her/himself, unless it concerns a Robertsonian translocation (13;21).
- Evidence of malignancy was found with the expectant mother at the time of requesting the NIPT.
- The expectant mother underwent a blood transfusion, stem cell, organ transplant, or immunotherapy in the past three months.
- The expectant mother is under the age of 16.
- The expectant mother – in the counselor’s opinion – is unable to understand and consent to the purpose of the research, possibly even with the help of an interpreter.
- The expectant mother does not have any Dutch health insurance contract or BSN (social security ID).
What certainty does the NIPT provide?
In comparison to the combined test, the NIPT does detect more cases of Down, Edwards or Patau syndromes in fetuses. Moreover, the results are more accurate, i.e. the NIPT sends fewer people for follow-up testing unnecessarily (less false positive tests).
Similar to the combined test, however, the NIPT is a screening test, not a diagnostic test. Because the NIPT uses DNA fragments from the placenta, an abnormal NIPT result requires chorionic villus sampling (CVS) or amniocentesis to confirm its findings. In some cases, it may happen that the placenta has a chromosome abnormality, but the fetus does not. Hence, in the event of an abnormal NIPT outcome, the expectant mother will be referred to a Center for Prenatal Diagnostics for further information and/or analysis, if she wishes. There she will receive information about any follow-up research. The time it takes for the results of a combined test to be known is shorter than the ones of the NIPT.
The NIPT screening test is currently only available in the context of a scientific national study: the TRIDENT-2. This implies that the expectant mother can only opt for the NIPT if she participates in the study, which requires signing a consent form.
Costs
Regardless of your insurance contract, the NIPT costs EUR 175, which is not reimbursed.
This RIVM owned website provides some more background information.
Besides the NIPT, there is always the possibility of having the combined test. It actually consists of a combination of two tests:
- A blood sample is taken after 10/11 weeks of pregnancy and this is taken to the lab
- The size of the fetal nuchal translucency (NT) is assessed between 11+2 and 13+4 weeks of pregnancy, by means of a medical ultrasound
In case of secondary findings, you will always be notified. During the assessment of the fetal nuchal translucency size, secondary findings may include defects or abnormalities in the abdomen, limbs or brain.
The results of the combined test will be communicated by the midwife, a few days after the NT procedure. When the blood sample was provided already prior to the NT procedure, the results are known quicker.
In case of abnormal results, additional follow-up testing is offered if desired.
In comparison to the combined test, the NIPT does detect more cases of Down, Edwards or Patau syndromes in fetuses. Moreover, the results are more accurate, i.e. the NIPT sends fewer people for follow-up testing unnecessarily (less false positive tests).
Similar to the combined test, however, the NIPT is a screening test, not a diagnostic test. The time it takes for the results of a combined test to be known is shorter than the ones of the NIPT.
Follow-up testing
When more certainty is required whether or not your baby has one of the above syndromes, follow-up testing is required, i.e. diagnostic testing instead of screening testing. A pregnant woman is eligible for these follow-up tests if, based on the NIPT or the combined test, she appears to have an increased risk of a child with Down, Patau or Edwards syndrome. She is also eligible for follow-up testing if there are other medical grounds that bring along an increased risk (where age does not count here).
The follow-up testing consists of one of the following tests:
- chorionic villus sampling (CVS) – a small sample of tissue is taken from the placenta and taken to the lab.
- Amniocentesis – a small amount of amniotic fluid is collected and examined.
In both a CVS and an amniocentesis procedure, there is a small risk of miscarriage; currently, this occurs in 1 to 3 in every 1000 tests.
Costs
Regardless of your insurance contract, the combined test costs EUR 168 (for one child), which is not reimbursed.
This RIVM owned website provides some more background information.
The 13-week ultrasound is a medical examination for physical abnormalities in your child. This ultrasound is very similar to the 20-week ultrasound. In both examinations, a specially trained sonographer examines your child extensively.
The 13-week ultrasound can be performed between 12+3 and 14+3 weeks of pregnancy. So from twelve weeks and three days up to and including fourteen weeks and three days of pregnancy.
Not all abnormalities can be detected yet: Some are too small to be seen at this term and some do not appear until later in the pregnancy. Imaging may also not be optimal for all pregnant women, for example due to overweight, scar tissue in the abdominal wall or position of the child. The 13-week ultrasound is not repeated if the sonographer could not see everything well. (This is in contrast to the 20-week ultrasound, which will be repeated in case of insufficient imaging)
During the 13-week ultrasound, the sonographer purposefully does not check whether it is a boy or a girl.
The sonographer will tell you the results immediately after the ultrasound. In 95 out of 100 pregnancies, the sonographer sees no indication of an abnormality. No further investigation is necessary.
Follow-up research
In about 5 out of 100 pregnant women, the sonographer sees something that could be an abnormality. It is not always clear whether it is indeed an abnormality, how bad the abnormality is and what this means for your child. Did the sonographer see anything abnormal? You can then opt for follow-up research.
If there is a suspicion of abnormalities, a pregnant woman can, if she and her partner so wish, be referred for a GUO (Advanced Ultrasound Examination) in the hospital. This is also an ultrasound that is done by a specially trained gynecologist.
Costs
This ultrasound is covered by your health insurance.
For more information, please refer onderzoekvanmijnongeborenkind.nl (some parts of the website are in English).
Scientific research
In the Netherlands you can only opt for the 13-week ultrasound if you participate in the scientific IMITAS study. This study investigates the advantages and disadvantages of the 13-week ultrasound.
This examination using medical ultrasounds looks at structural (physical) abnormalities of the unborn child. Preferably, the SEO is carried out around 20 weeks of amenorrhea (between 18+0 and 22+0 weeks of pregnancy). Hence, it is also known as the 20-week anomaly scan. We aim to complete the SEO before 21+0 weeks. The reason for this is that if abnormalities are found, any follow-up testing is often time-consuming. Once the results of the follow-up tests are available, sufficient time may need to be available to process the new information and to decide whether or not to terminate the pregnancy.
The SEO at a gestational age of 18 to 20 weeks does not find all abnormalities. It depends on the nature of the abnormality how likely it is that it can be seen. Some are too small to be seen at this time and some do not appear until later in the pregnancy. In some cases, the ultrasound imaging may not be optimal either, e.g. due to overweight, scar tissue in the abdominal wall or the current position of the baby.
A normal result of the SEO is reassuring, but it does not rule out that there are abnormalities in the fetus. Not all physical abnormalities can be seen with a medical ultrasound around 20 weeks of pregnancy. In addition, the SEO is not a genetic research either and, for example, mental limitations cannot be determined. It is important for the expectant parents to realize the limitations of SEO.
Pregnant women who decide to have an SEO carried out opt for an examination of the entire baby. The expectant mother cannot choose to not want to be informed about certain abnormalities. In addition to structural abnormalities, other relevant abnormalities may be found that require further analysis/tests (so-called secondary findings).
Follow-up tests
If the SEO rises suspicion of abnormalities, you may be referred to the hospital to carry out a GUO (“Geavanceerd Ultrageluid Onderzoek”, or advanced ultrasound examination). A specially trained gynecologist will perform this examination. There are two types:
GUO type 1: Expectant mothers who need a GUO based on their medical background, because there is a higher risk of abnormalities, are eligible for type 1. They can skip the screening stage.
GUO type 2: Expectant mothers who are referred by their midwife because there is a suspicion of an abnormality are eligible for type 2.
Costs
The SEO is fully covered by your health insurance.
This RIVM owned website provides some more background information.
Choose consciously
Many prospective parents find it difficult to make a choice regarding the above. We will explain the tests, if you wish, during a special consult (a counseling consultation) after your intake and hope that this will make your choice a little easier. In addition, the expectant parents receive information leaflets so that they can read them together at home in peace. Sufficient time for reflection is important for making a right choice and of course we are always willing to provide even more explanation during this reflection period.
Please do realize that not all possible abnormalities can be discovered or investigated before childbirth. If examinations and tests indicate that the chance of a child with – for example – Down syndrome is small, it may very well still have this or even another condition.
For more information regarding prenatal screening and follow-up tests, please also refer:
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