Five questions and answers about Preimplantational Genetic Diagnosis

What is Preimplantational Genetic Diagnosis?

It consists of analyzing one or more cells of the embryo before it is transferred to the mother’s uterus in an in vitro fertilization process, in order to detect whether the embryo in question is a carrier of a specific genetic disease that is the subject of the study.

What information is obtained with Preimplantational Genetic Diagnosis?

Basically, the information obtained refers to whether the embryo analyzed is a carrier of some of the affected genes, which are responsible for the development of certain genetic diseases, sometimes serious. The number of chromosomes, certain chromosomal alterations and the sex of the embryo can also be reported.

What diseases can be prevented thanks to Preimplantational Genetic Diagnosis?

Multiple genetic diseases can be prevented, some better known such as hemophilia, fragile X syndrome, certain neurodegenerative diseases such as Duchenne syndrome, and many others less well known. More and more genetic diseases can be identified in affected parents or carriers through advances in molecular genetics in DNA studies and through massive sequencing methods.

In addition to the study of the embryo to rule out that it is a carrier of one of the many genetic diseases mentioned above, it is also used as a method not only for diagnosis, but also for screening in certain clinical situations that may be due to chromosomal disorders. In this case, no attempt is made to identify any affected gene, but rather a chromosomal study of the embryo is carried out to see if anomalies are detected that could be the cause of repeated implantation failures in in vitro fertilization (IVF) processes, in cases of repeated miscarriages, in IVF failures due to advanced maternal age or in certain cases of severe male factors. These indications are not so well recognized by the health authorities and scientific societies at the international level, since in some cases a real benefit has not been demonstrated, but they can provide in some cases a greater probability of successfully completing an in vitro fertilization process. There is unanimity in considering Preimplantation Genetic Diagnosis as a great advance in science, with regard to the screening of genetic diseases transmitted to the embryo by one of the progenitors.

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Can the analysis of embryos affect their development?

The removal of one or more cells from the embryo is, in a certain way, a method that is potentially harmful to the embryo. It is not excluded that it could influence the viability of the embryo. This does not mean that the method increases the probability that the implanted embryo will give rise to the formation of a fetus with abnormalities, since the cells at this stage are totipotent. This means that an embryo can stop its development when tested, but if it does not, the future fetus will not suffer any abnormality because it has been tested.

Which couples should undergo Preimplantation Genetic Diagnosis?

As can be deduced from the above, those couples in which one or both members are carriers of a genetic disease and who are aware of it should undergo this method. Unfortunately, in some cases they are not aware of it, since the disease may not have manifested itself in any member of the family up to that moment.

But not all diseases are susceptible to this treatment, since it is a method that has a certain complexity and is usually expensive. The Assisted Reproduction Law makes explicit reference to the fact that this treatment will be applied only in cases in which serious and early onset diseases can be transmitted to the offspring, and which are not susceptible to being successfully treated after birth. There are diseases in which this treatment should not be applied because they do not meet these assumptions, and others, of more uncertain significance or variable in each case in terms of severity, in which permission must be requested from the National Commission on Assisted Reproduction to see if in that case the treatment can be applied.