Preimplantational genetic diagnosis PGD

Detection of monogenic diseases (PGD)

These tests are aimed at detecting diseases caused by point mutations that can be inherited from parents. They involve a pre-cycle informativity study performed by analyzing the DNA of the prospective parents and, in specific cases, of first- or second-degree relatives. Once the specific mutation has been identified, the in vitro fertilization cycle is performed, the embryos are biopsied, and the cells are sent to the genetic analysis laboratory where, through molecular studies, the specific mutation being sought is detected. Once the results are received, embryologists prepare for transfer those embryos that have been reported as disease-free.

It should be noted that this technique cannot be used for any type of disease. The law of assisted reproduction in our country is very restrictive and only allows the selection of embryos whose pathology meets the following characteristics:

• Early onset disease
• Incompatible with life
• Not amenable to medical treatment

Based on this, there is already a list of pathologies for which embryo selection is allowed (such as cystic fibrosis, thalassemias,…) but for many others it is necessary to request express authorization from the National Commission on Assisted Reproduction. It is a procedure that can be relatively lengthy but is necessary for all those diseases not yet included in the list.

Detection of aneuploidies (PGS)

They are aimed at detecting numerical or structural chromosomal alterations. It is a much simpler process than the previous one since, due to the nature of the patients susceptible to this technique, the previous analyses required are only karyotyping and/or FISH of spermatozoa as a general rule.

Patients susceptible to this treatment are:

• Patients with previous IVF cycles with good quality embryos without achieving pregnancy.
• Patients with repeated miscarriages
• Patients with implantation failure
• Patients with altered karyotypes
• Patients with altered spermatozoa FISH
• Previous pregnancies with detection of fetal chromosomal abnormalities
• Patients with high maternal age

One of the alterations that can be detected by performing this study is the trisomy of chromosome 21 (Down syndrome); in this case it is observed that the embryo, instead of having two chromosomes of the 21st pair, has 3. A similar picture is observed for Patau’s or Edwards’ syndrome, as well as chaotic alterations that are usually associated with implantation failure or repeated miscarriages.

Procedure

The PGD technique is the result of the combination of in vitro fertilization, pre-embryonic cell biopsy by means of micromanipulation and cytogenetic and molecular diagnostic techniques.

• Preliminary phase: in this phase, genetic characterization tests of the disease to be diagnosed or karyotyping of patients are performed, in order to have as much information as possible prior to the application of PGD, either for monogenic diseases or chromosomal alterations.
• Embryo procurement: this involves obtaining the embryos that will be the object of the diagnosis. They must be produced “in vitro” by assisted reproduction techniques even if the couple does not present any type of reproductive anomaly that prevents natural reproduction.
• Embryo biopsy: embryo biopsy is performed on the third day after fertilization, when the pre-embryo is at the 6-8 cell stage, or on the fifth day, when the embryo is at the blastocyst stage (depending on the case). It consists of removing a cell or a group of cells without compromising the normal development of the embryo. Once the biopsy has been performed, the embryos are placed back in the incubator, where they are kept in culture until the result of the diagnosis is obtained and their possible transfer and/or vitrification is assessed.
• Genetic diagnosis and embryo transfer: the biopsy obtained is processed for analysis and submitted for genetic study. The result obtained from the genetic analysis indicates which embryos are transferable (free of the disease or without chromosomal alterations) and which are not, and the embryos are then transferred or vitrified.

Specific PGD laboratory

The value of the single sample”. That is our motto when performing a technique of this type. Embryologists who biopsy embryos must have specific training in this field to be able to perform such a critical and delicate process with guarantees, as is the case of our Senior ESHRE embryologists. Therefore, entrusting the subsequent analysis of this valuable material cannot be entrusted to just any analytical laboratory. At the ERGO Clinic we only trust the best, those who have been analyzing thousands of embryos from all over the world for years and who are accustomed to receiving representative cells sent with all that love.

Probably your case is special; it is normal, genetics is as capricious as it is beautiful. Come and see us, explain us your case and we will inform you naturally on how to help you. A free appointment, with no obligation and with the guarantee that you will be attended by embryologists who are experts in reproductive genetics.