The new genetic diagnosis techniques are undoubtedly one of the most important advances in medicine in recent years, being even more remarkable in Reproductive Medicine. After the “Human Genome Project”, back at the beginning of this century, tools were developed that today make it possible not only to detect embryos with alterations in the number of chromosomes (known as “aneuploidies”) but also to prevent genetically transmissible diseases. So what are the genetic studies that could be carried out in reproduction?
Through a blood test, the “karyotype” makes it possible to determine possible chromosomal alterations in the parents (or in the sperm or egg donors), which could be the cause of recurrent miscarriages, fertilisation failures or chromosomal anomalies in the offspring.
Carrier panel study
This is also done through a blood test and allows the determination of pathogenic variants (commonly known as “mutations”) in a number of genes that can cause disease in offspring.
All people have mutations in at least 3 to 6 of the more than 20,000 genes that make up our genome. This is not a problem for us because genes go “in pairs”, and it would take 2 altered genes for us to be suffering from one of these so-called “recessive” diseases. The importance of knowing which genes we have altered lies in the fact that, if our partner shares the same mutation, we would run the risk of transmitting this disease to our baby, and this can be prevented today. In the case of treatment with donated sperm or eggs, this is also important in order to be able to “choose” a donor who does not share the same mutation, which is known as “genetic matching”.
PGT (Preimplantation Genetic Test) or PGD (Preimplantation Genetic Diagnosis)
PGT is a more complex technique with which, by means of a biopsy performed on the embryos obtained in the laboratory through IVF treatment, we can determine those that have an alteration in the number of their chromosomes.
Chromosomally abnormal embryos are NOT transferred because they are either incapable of implanting, or they implant and generate a first trimester miscarriage, or they give rise to babies with chromosomal diseases (e.g. Down’s Syndrome or Trisomy 21).
Thus, by being able to select chromosomally healthy embryos for transfer to the uterus:
- the number of transfers (which we already know in advance will not be successful) is reduced.
- the risk of miscarriages in the first trimester of pregnancy is decreased
- the risk of having a baby with a chromosomal disease is reduced.
There is also a special PGT called PGT-M, in which the aim is to study the alteration of a specific gene in the embryo, in those cases in which it has already been detected that this mutation is shared in the parents through the study of the Carrier Panel.
As always, each case must be considered on a case-by-case basis. None of these tests are compulsory, nor are they part of the routine fertility treatment, but it is important that patients are aware of them and have complete information that allows them to decide whether or not to undergo them. Proper genetic counselling and knowledge of these techniques will give patients the power to determine what they feel is best for them.