Invasive diagnostics
Invasive diagnostics
Amniocentesis, chorionic villus sampling, cordocentesis
In addition to the various sonographies, there are also prenatal examination methods that involve a minor intervention. These are summarised as invasive diagnostics. There are three different examinations: puncture of amniotic fluid (amniocentesis), removal of placental tissue (chorionic villus sampling) or blood sampling from the umbilical cord (cordocentesis).
The first two tests are explained in detail below. What they have in common is that they are the only way to rule out the chromosomal disorder Down's syndrome with certainty. Both procedures are associated with the (albeit very low) risk of miscarriage.
The third test, blood sampling from the umbilical cord, is rarely used in prenatal diagnostics today. This is also due to the fact that it is very difficult to perform and requires an experienced surgeon. We have the necessary experience, which is why cordocentesis is still one of our examination methods when necessary.
Speaking of experienceWe have plenty of them across the entire spectrum of invasive diagnostics. From 50 punctures a year, you are generally regarded as an experienced surgeon, we carry out around 300 a year. This means that we cannot accept the common opinion that the removal of placental tissue (chorionic villus sampling) is more dangerous than amniocentesis. For us, both have a low, equally low risk.
It should also be mentioned that the total number of invasive examinations is declining due to the now reliable first trimester screening, although this decline is almost entirely due to amniocentesis. The reason for this is that chorionic villus sampling is favoured by doctors as it provides profound test results at a much earlier stage.
Before all invasive prenatal examinations, we consider detailed genetic counselling to be advisable.
Amniocentesis
Amniocentesis
The analysis of the amniotic fluid includes the examination of the chromosomes and the determination of the alpha-fetoprotein as standard. This is a foetal protein whose concentration is increased in the amniotic fluid in the case of clefts of the back or abdominal wall. If there are known hereditary diseases in the family, in which usually not a whole chromosome but only small sections on the chromosome - the so-called genes - are altered, it is also possible in some cases to check these. This is called molecular genetic testing.
It is impossible to rule out all conceivable diseases. In rare cases, despite careful performance, there may be no or an unclear test result, e.g. because the cells do not multiply properly or different chromosome distributions are found. This may result in the amniocentesis having to be repeated.
Before each amniotic fluid analysis, a detailed ultrasound examination is carried out. The skin is then disinfected to prevent the introduction of bacteria or viruses.
A thin needle is then inserted into the desired region and the amniotic fluid sample is taken through an attached syringe. This is done under ultrasound guidance to ensure that the desired goal is achieved quickly and reliably. In addition, the risk of unintentional injury to the foetus or neighbouring organs can be minimised through visual monitoring.
The pain during this examination is experienced by the women concerned as a somewhat unpleasant pressure in the lower abdomen and is compared to that of a blood sample or a vaccination. The administration of a painkiller or a local anaesthetic is therefore not necessary.
The foetal cells present in the amniotic fluid sample are then multiplied in an appropriate laboratory. As soon as enough cells have grown, they can be analysed. This takes an average of 14 days.
It is also possible to obtain the result for individual chromosomal disorders such as Down's syndrome within 24 hours using a rapid test procedure (known as FISH diagnostics). These rapid tests are not usually included in the catalogue of services provided by statutory health insurance companies and must be paid for by the patients themselves. We will be happy to answer any specific questions you may have.
We would also like to draw your attention to possible complications. Although these occur rarely, they cannot be ruled out in individual cases despite careful performance of the examination. A miscarriage occurs in approx. 0.3 - 0.5 % of punctures. It is very rare for there to be a temporary loss of amniotic fluid or bleeding; in most cases, the pregnancy can be maintained by taking appropriate measures such as rest or inpatient monitoring.
Download form (PDF)
You are welcome to print out this form in advance.
Chorionic villus sampling
Chorionic villus sampling
The chorion is a layer of cells on the outside of the amniotic sac. The chorion cells develop into chorionic villi, which go on to form the foetal part of the placenta. Although these cells are not part of the unborn child, they are usually genetically identical.
As chorionic villus sampling can be performed from the 11th week of pregnancy, it is suitable for patients who want the results as early as possible.
However, it is not possible to rule out all possible diseases. Sometimes the sample does not contain enough tissue so that - although very rarely - direct preparation must be dispensed with and the long-term culture awaited. Occasionally, it can also happen that insufficient growth is achieved in the long-term culture - so-called culture failures. In such cases, the chorionic villus sampling can be repeated or (depending on the gestational age) an amniocentesis can be performed.
Chromosome mosaics occur rarely. In this case, different chromosome patterns are found in the cells in the direct preparation and/or long-term culture. Additional procedures such as an amniocentesis or umbilical cord puncture may be necessary for further clarification. Each chorionic villus sampling is preceded by a detailed ultrasound examination. The subsequent skin disinfection serves to prevent the introduction of bacteria or viruses.
A thin needle is then inserted into the desired area under ultrasound guidance in order to suck out some of the villi using a syringe. This ensures that the targeted region is reached quickly and precisely. In addition, the visual control minimises the risk of unintentional injury to neighbouring organs. The risk of an injured foetus is in any case much lower with placental tissue sampling than with amniocentesis, as there is no penetration into the amniotic sac.
The examination is not really painful but quite unpleasant - that is why we also perform a local anaesthetic.
Complications occur only occasionally, but cannot be completely ruled out despite careful performance of the examination. A miscarriage occurs in approx. 0.5 % of punctures. Bleeding occurs very rarely, in most cases the pregnancy can be maintained by taking appropriate measures such as rest or inpatient monitoring.
Download form (PDF)
You are welcome to print out this form in advance.
