Chorionic villus sampling is a prenatal diagnostic procedure in which tissue from the placenta is examined. The aim of the examination is to identify genetic abnormalities or disorders in the foetus. Experienced specialists advise and support expectant mothers and fathers before and during this prenatal examination.
Below you will find further information and selected specialists for a chorionic villus sampling.
Chorionic villus sampling, like amniocentesis, is part of prenatal diagnosis. This refers to procedures for detecting diseases in the womb. Chorionic villus sampling is also known as chorionic biopsy, choriocentesis, placental puncture or placental puncture.
It is an invasive diagnostic procedure. This means that not only a risk assessment is carried out, as is the case with first trimester screening, for example. During a chorionic villus sampling, tissue cells are removed and examined.
Chorionic villus sampling therefore enables the reliable exclusion or diagnosis of a hereditary disease, such as Down's syndrome.
The tissue cells are taken from the placenta. This tissue is of embryonic origin, even if it does not belong to the embryo itself. Therefore, the genetic information in the cells of the placenta is (largely) identical to that of the fetus.
Chorionic villus sampling can be carried out from the 12th week of pregnancy. It is therefore possible much earlier than an amniocentesis or umbilical cord puncture.
A chorionic villus sampling is not part of routine prenatal care, but is only carried out at the express request of the parents.
The prerequisite is usually a previous examination, such as
with an abnormal result. The examination can also be useful in the case of certain diseases in the family.
Beforehand, the doctor must inform the parents about
in detail and in a way that is easy to understand . As a rule, there is no causal therapy for the disorders that can be detected with a chorionic villus sampling. The prospective parents should therefore be aware that they may have to make a decision about the continuation of the pregnancy.
Nevertheless, diagnostics can also be useful beyond the decision for or against pregnancy. It gives parents who decide in favor of the child time to prepare and inform themselves.
In some cases, knowledge of the child's disability/disease enables parents and doctors to create better conditions for the child's optimal development prenatally and during and after delivery without delay. This is the case, for example, with hemophilia (bleeding disorder) or rare metabolic disorders.
Before the puncture, a thorough ultrasound examination is carried out. This is used to assess the fetal organs and the position of the placenta. The biopsy can generally be performed via
be performed.
Today, biopsies are predominantly performed transabdominally. A thin biopsy needle is inserted through the abdominal wall and past the amniotic sac into the placenta under ultrasound guidance. Some tissue is then sucked into the needle.
The puncture only takes about 20 seconds and is hardly painful.
During a chorionic villus sampling, cells are removed from the placenta under ultrasound guidance © Sora_Kobayashi | AdobeStock
The tissue removed is cultivated (further multiplied) and examined in the laboratory. The cells are usually examined under a light microscope after 24 hours. This allows the number and shape of the chromosomes to be assessed. In this way, deviations in the number of chromosomes can primarily be determined:
After a few days, the cell culture can be used for a molecular biological DNA analysis.
Important to know: The examination only tests for specific genetic changes for which there are reasonable grounds for suspicion. These include, in particular, fetal malformations and a history of genetic problems. The entire spectrum of possible hereditary diseases is not tested for. The foetus may therefore have other diseases that cannot be detected during the chorionic villus sampling.
The results of chorionic villus sampling are generally very reliable. This is particularly true for common chromosomal disorders such as Down's syndrome.
In very rare cases, there are cells with different genetic make-up in the placenta (the technical term for this is placental mosaicism). In this case, an additional amniocentesis should be performed for further assessment.
The slightly increased risk of miscarriage is the greatest risk associated with any invasive diagnostic procedure. This has decreased significantly in recent years. Current evaluations of large amounts of data show that the additional risk of miscarriage is around 0.2 percent. Of course, the experience of the examiner is of great importance here.
Rhesus-negative mothers run the risk of rhesus incompatibility (with a rhesus-positive child). In such a case, the mother forms antibodies against the fetus as soon as the child's blood enters her bloodstream. This may be the case when the biopsy needle is withdrawn.
Rhesus prophylaxis (a type of vaccination) carried out immediately after the chorionic villus sampling prevents this immune reaction.
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