Chorionic villus test
- During a chorionic villus test the gynaecologist takes a very small piece of the placenta away with a hollow needle.
- In the lab part of the chorionic villi is kept in culture as a back-up in order to have sufficient material to be able to examine. In order to be able to start that process around 15 mg of chorionic villi are needed.
- The other part is used for direct chromosomal, molecular and/or biochemical testing. First of all the material from the foetus is separated from that of the mother under the microscope. After this the DNA or the proteins are extracted manually.
- On DNA that has been extracted from the villi, detailed chromosomal testing will be carried out in order to be able to detect both large changes (such as trisomy, monosomy) and small changes (deletions, duplications).
The result is usually known after around ten working days, unless the concentration of DNA was too low and the cells first have to be cultured before sufficient DNA can be extracted from them.
For some molecular and biochemical analysis a direct diagnosis is not possible because of the complexity. Then sufficient material has to be available and that can only be obtained after a sufficiently long culture.