Prenatal
There are also limits to chromosome analysis:
If, for example, changes occur in very small chromosome segments or only individual genes are altered, this cannot be recognised under the microscope.
- If the body cells of the unborn child carry a so-called mosaic (a different set of chromosomes), this cannot be recognised with certainty (although this is only very rarely the case)
- Although we check suspected cases using contamination exclusion, it cannot be ruled out with absolute certainty that maternal cells have grown in the incubator instead of foetal cells (although this occurs in less than 1% of cases)
- In rare, unfavourable circumstances, the test results for twin pregnancies may only apply to one twin
- The test result may be available later than usual because the cell cultures grow very slowly (in a few cases)
- In rare cases, no analysis is possible. In this special case, we will discuss the individual further procedure with you and your gynaecologist. In some circumstances, for example, a repeat puncture may not be necessary if a rapid test has been performed.
Questions or appointments?
Do you have further questions on the subject of "prenatal genetics" or would you like to make an appointment at our practice for prenatal medicine and genetics?
Amniocentesis (amniotic fluid puncture)
For pregnant women or couples who wish to have children, amniocentesis is still the most common test method used today to rule out genetic abnormalities in the unborn child. In this examination, foetal cells are taken from the amniotic fluid and their genetic material is then analysed. In this way, numerous chromosomal disorders can be ruled out with a high degree of certainty. In addition, other diseases or malformations can be ruled out with a high degree of certainty based on the amniotic fluid analysis (e.g. spina bifida aperta, the so-called open back).
Younger pregnant women are also increasingly opting for an amniocentesis if they personally feel that their individual risk (age risk or determined by a first trimester screening) is too high. The decision as to whether an amniocentesis should be carried out can be made by pregnant women or parents-to-be regardless of the individual risk findings for a possible chromosomal disorder in the child.
However, in our practice we only carry out punctures when (at least) the 15th week of pregnancy has ended, as amniocentesis in the first weeks of pregnancy can lead to more frequent complications.
During an amniocentesis, a very thin hollow needle (the outer diameter is around 0.7 mm) is inserted into the amniotic cavity. This process takes place under constant Ultrasound control so that injury to the foetus can be ruled out. Approximately ten to 15 millilitres of amniotic fluid are removed, which corresponds to less than ten percent of the total amount of amniotic fluid. The loss of this small amount of amniotic fluid can be quickly compensated for by the amniotic cavity. The procedure itself only takes about one to two minutes and usually only causes a slight pulling sensation in the abdomen of the women being examined. Thanks to the elastic tissue, the tiny puncture channel closes again immediately after the puncture. Cultures are created using the cells obtained from the amniotic fluid. The growth and multiplication of the cell cultures can take some time. On average, however, the result of amniocentesis is available within two weeks. However, an additional rapid test (PCR) can reliably rule out the most common chromosomal abnormalities (trisomy 13, 18, 21) within one working day of the puncture. The sex of the child can also be reliably determined by PCR. No further amniotic fluid needs to be taken for this additional test, as only a minimal amount of genetic material (DNA) is required.
The costs for the PCR rapid test are only covered by statutory health insurance companies in the case of serious abnormalities and are not always covered by private insurers either. To ensure that clefts of the spine (spina bifida aperta) can be ruled out with a high degree of probability, the protein alpha-fetoprotein (AFP) is determined in the amniotic fluid.
There is a small risk that an amniocentesis could cause a miscarriage.
In our Cologne practice, we have performed more than 3,000 amniocenteses in the last 8 years.
The frequency of miscarriages increased by an average of three losses per 1,000 pregnancies. In very rare cases, amniotic fluid may be lost through the vagina. In most cases, however, this defect in the amniotic sac closes again and the pregnancy usually continues without complications. An infection or haemorrhage due to amniocentesis occurs even less frequently. Your individual risk of complications will be clarified and assessed in an ultrasound examination before the puncture.
A study involving 35,000 women has shown that taking the antibiotic azithromycin in the last three days before the puncture can reduce the risk of miscarriage due to the procedure to well below one in 1,000. Taking this antibiotic is also safe during pregnancy due to its few possible side effects. The medication is intended to prevent existing infections of the cervix or vagina from being stimulated and provoking premature rupture of the membranes. Publications on the administration of azithromycin during pregnancy do not show any increased malformation rates. Even when the drug was administered in very high toxic doses in animal experiments, no malformations were observed.
Immediately after the amniocentesis, you should lie down and rest for at least half an hour. We offer you our relaxation area for this purpose. Should complications occur in very rare cases, these occur in particular within the first 24 hours after the puncture. We therefore recommend that you rest on the day of the puncture and the next day, mainly lying down. Ideally, you should stay at home and avoid heavy physical exertion such as heavy lifting, frequent climbing of stairs or sport. If you are working, we advise you to ask your gynaecologist to issue you with a sick note for these two days. You should also visit your gynaecologist for a check-up one or two days after the amniocentesis. If you lose blood or fluid after a puncture, or suspect this, you should definitely visit your doctor or a clinic. The same applies to severe lower abdominal pain or any other symptoms. If there are no complications after the amniocentesis, you can safely resume sporting activities one week later. Air travel and sexual intercourse are also possible again. Of course, this only applies if your doctor has not already given you a different recommendation for your behaviour after the puncture.
Chorionic villus sampling
The placenta (placenta, chorion in early pregnancy) is derived from the fertilised egg, which is why cells obtained from it can be used to analyse the chromosomes of the child.
If a chromosome analysis is desired or indicated very early in the pregnancy, a chorionic villus sampling makes sense.
In our practice, we perform a chorionic villus sampling from the eleventh week of pregnancy at the earliest. The risk of complications is higher before this, as the embryo's organ development is not yet complete. In contrast to an amniocentesis, a chorionic villus sampling does not provide any information about clefts of the spine (spina bifida aperta).
- There is a desire on the part of the mother or expectant parents for an early diagnosis
- There are abnormalities in the ultrasound image
- A high risk was detected in the first trimester screening
- There are already hereditary diseases or metabolic disorders in the family environment
During a chorionic villus sampling, a thin hollow needle (outer diameter less than 1 mm) is inserted into the placenta so that small tissue cells can be removed. This procedure takes place under constant ultrasound monitoring. The procedure often only takes one to two minutes. The women undergoing the procedure usually feel a pulling sensation in their abdomen during the puncture.
Cultures are created from the tissue removed. As these cultures need some time to multiply and grow, the result of the chorionic villus sampling is available after approximately ten days.
A short-term test is carried out in addition to every chorionic villus sampling. This test can rule out the most common chromosomal abnormalities just one to two working days after the procedure.
More than 800 chorionic villus biopsies have been performed in our practice since 2008.
This resulted in an increase in the natural miscarriage rate of around 0.3 per cent, which means three miscarriages per 1,000 pregnancies. However, it should be noted that natural miscarriages also occur more frequently in this early stage of pregnancy than in the later stages of pregnancy.
After a chorionic villus sampling (as well as after an amniocentesis or umbilical cord puncture), we recommend that you lie down and rest in our relaxation area for at least half an hour.
Although complications are very rare, they are possible, especially within the first 24 hours after the procedure. We therefore advise you to take it easy on the day of the procedure and the next day and to stay at home if possible.
You should also avoid heavy physical exertion such as sport, frequent climbing of stairs or heavy lifting and instead rest mainly lying down.
If you are working, we recommend that you take a sick note from your gynaecologist for these two days. You should also visit this doctor for a check-up one to two days after the puncture.
If you lose blood or fluid after a chorionic villus sampling, or suspect this, you should definitely consult your doctor or a clinic. The same applies to severe lower abdominal pain or any other complaints.
If there are no complications after the chorionic villus sampling, you can safely resume sporting activities one week later. Air travel and sexual intercourse are also possible again. Of course, this only applies if your doctor has not already given you a different recommendation for your behaviour after the procedure.
Umbilical cord puncture
In the case of some diseases of the unborn child, an umbilical cord puncture may be necessary. This procedure allows blood and medication to be introduced into the child's circulation. For diagnostic or therapeutic reasons, this puncture is only possible after the 18th week of pregnancy.
- If there is a blood group incompatibility
- If there is an infection during pregnancy
- If the child has anaemia (anaemia)
- If a paediatric metabolic disorder is suspected
- If there were abnormalities in the ultrasound for late chromosome analysis
After an umbilical cord puncture (as well as after an amniocentesis or chorionic villus sampling), we recommend that you lie down and rest in our relaxation area for at least half an hour.
Although complications are very rare, they are possible, especially within the first 24 hours after the procedure. We therefore advise you to take it easy on the day of the procedure and the next day and to stay at home if possible.
You should also avoid heavy physical exertion such as sport, frequent climbing of stairs or heavy lifting and instead rest mainly lying down.
If you are working, we recommend that you take a sick note from your gynaecologist for these two days. You should also visit this doctor for a check-up one to two days after the puncture.
If you lose blood or fluid after an umbilical cord puncture, or suspect this, you should definitely consult your doctor or a clinic. The same applies to severe abdominal pain or any other complaints.
If there are no complications after the umbilical cord puncture, you can safely resume sporting activities one week later. Air travel and sexual intercourse are also possible again. Of course, this only applies if your doctor has not already given you a different recommendation for your behaviour after the puncture.
foetal DNA test
During pregnancy, some of the DNA from the foetal part of the placenta passes into the mother's blood. Information about the condition of the baby's chromosomes can be obtained from the DNA. We offer laboratory tests in which the baby's DNA is extracted from a sample of the mother's blood. These are non-invasive prenatal tests (NIPT). This means that these tests are safe for you and your baby. To carry out the test, you must be given a Ultrasound examination only some blood needs to be taken.
The foetal DNA tests can be used to examine the DNA for the risk of the following disorders:
- Trisomy 21 (Down syndrome)
- Trisomy 13 (Pätau syndrome)
- Trisomy 18 (Edwards' syndrome)
- Monosomy X (Turner syndrome)
More information at FOETAL DNA TESTS.
Array CGH examination
Array CGH analysis is a computer-aided analysis method that can detect the smallest chromosomal changes that were not detected by previous tests. Array CGH analysis is therefore a useful extension and addition to classic chromosome analysis, which can provide new findings in the case of inconspicuous previous genetic findings.
Array CGH analysis can provide reliable information about numerical chromosomal changes within just a few days. In addition, it is also possible to obtain much more precise information about microchanges in the genome using array CGH analysis. Accordingly, array CGH is developing into a very important method of analysis in prenatal diagnostics. Array CGH chip analysis has also become an important method for the examination of physically or mentally impaired children (postnatal examination).
In the case of abnormalities in prenatal diagnostics, the use of an array CGH analysis must currently still be individually authorised by the cost bearers. If there are indications of developmental disorders that cannot be detected using chromosome analysis, array CGH analysis is generally used. In the case of unremarkable findings, the Array-CGH chip analysis can be carried out as an optional service.
Procedure of the Array-CGH examination
For the array CGH test, part of the genetic material (DNA) must be obtained by puncturing the amniotic fluid or umbilical cord or by a chorionic villus sampling. The DNA is then attached to a chip and labelled with fluorescent dyes. This makes it possible to recognise whether certain areas of the unborn child's genome have been lost or contain surplus information.
