Developing the PGT test
As soon as the PGT clinic has all the necessary reports and samples and therefore knows which genetic abnormality is concerned, the development of the PGT starts. The aim of this is to be able to make, efficiently, a reliable genetic diagnosis from one or more cells of an embryo.
What types of PGT are there?
The different types of PGT serve a different aim:
- In monogenic disorders the PGT can detect an abnormality from one gene.
- In chromosomal abnormalities the test serves to detect abnormalities in the chromosomes (number, structure). Therefore the PGT clinic can...
- ... count (certain) chromosomes
- ... look at the shape of the chromosomes to make an analysis of the normal/balanced segregation pattern in translocation chromosomes
- In X-linked conditions thanks to PGT the sex of the embryos can be determined. Depending on the condition therefore only female or only male embryos will be eligible for placement. In most X-linked conditions the PGT clinic is, however, able to carry out a mutation-specific analysis and therefore place both healthy male and female embryos.
- There is also HLA typing. This special PGT investigates which embryos have the same tissue type as an existing, seriously ill child of the same parents. Children with a certain (fatal) blood or immune disease can sometimes be cured owing to the transplantation of blood stem cell or bone marrow cells. That is only possible if the transplanted cells are HLA-compatible with the cells of the sick child. If they are not compatible, they are discarded. A baby born after an HLA treatment can in other words be a donor to save a sick brother or sister. In the media such a baby is also called a ‘saviour baby’ or a ‘donor baby’.
Read more below.
How long does it take to develop the test?
The development of a PGT can take a few weeks up to a few months, depending on the condition and the type of analysis.
To date, each illness requires a separate, often individualised approach. In order to be able to develop the test, the CMG first needs a genetic blood analysis of both prospective parents. In a monogenic disorder frequently a blood or DNA test is also carried out in family members. In so doing the PGT clinic then investigates how the faulty DNA code is inherited and where precisely in the embryo’s DNA the fault is to be looked for.
For some conditions the PGT clinic has already developed a PGT with a number of markers or a genome-wide PGT is available. Therefore it is always first investigated whether you fit a test like this. If that is the case the test can be worked out in a reasonably short timeframe, in two to three months. In very exceptional cases the PGT clinic has to develop a new test. That takes rather longer, around six to eight months.
!!! Avoid a spontaneous pregnancy
As soon as the PGT clinic starts to develop the test, they will ask you to only have protected intercourse and to stop any attempts at becoming pregnant spontaneously. This is because the development of a test is individual and expensive. Moreover, in a spontaneous pregnancy you will have no prior genetic diagnosis of the baby you are expecting. If you nevertheless become pregnant in the period during which the test is being developed, you can of course decide to have a prenatal diagnosis performed.