If there are embryos with an inadequate number of chromosomes, which are called Aneuploid embryos (PGT-A)
If there are embryos with a recessive or dominant genetic disease (PGT-M)
If there are embryos with translocations in their chromosomes (PGT-SR)
Preimplantation Genetic Testing of Embryonic Aneuploidies
“Aneuploidies” are partial or total gains or losses of chromosomes. The PGT-A serves to detect them since aneuploid embryos can lead to implantation failure, arrest in their development and spontaneous pregnancy loss. In general, these originate during the formation of reproductive cells, and are more frequent as the maternal age advances.
PGT-A is indicated in couples with:
Advanced maternal age
Repeated pregnancy losses
Recurrent implantation failures
Certain cases of male infertility
What are the benefits?
Decreace of abortion rates.
Higher transfer pregnancy rates.
Greater chance of having a healthy baby.
Fewer transfers to achieve a pregnancy.
Chromosome normality means having 23 pairs of chromosomes:
One less chromosome or an extra one leads to health and development problems:
Preimplantation genetic testing for monogenic diseases
Monogenic diseases are those caused by an alteration in a certain gene (some examples of them are cystic fibrosis, thalassemias and Fragile X). To avoid the transmission of the disease to the offspring, the PTG-M study is performed on the embryos.
If, after a preconception genetic test for recessive diseases of the parents, it is detected that both have the same genetic mutation, this means that there is an increased risk for the offspring with this disease. In these cases, if the embryo inherits two mutated copies of the
same gene, the baby will have a greater chance of suffering from the disease. Therefore, the PGT-M can be done to select those embryos that do not present the two copies of the same mutated gene.
In the cases of PGT-M of monogenic diseases, an informative study (“gene template” of the parents and sometimes also of other related relatives) must be carried out prior to the PGT-M cycle to confirm that the diagnosis is feasible and adjust the technique to each particular case.
Analysis of structural chromosomal abnormalities in embryos.
A chromosomal translocation means that a portion of a person’s chromosome is in an “abnormal” place; in other words, it is “translocated” within the genome, to a different position than the one it should be in. It can occur in anyone, without having any clinical manifestation.
The presence of a chromosomal translocation (Robertsonian translocations, reciprocal translocations and inversions) in a member of the couple, can carry embryos with that translocation or more serious issues; witch means association with conceiving difficulties, miscarriages or congenital malformations. The application of PGT-SR in the embryos of these couples is very useful to successfully achieving a pregnancy.
That is why it is recommended for people who are diagnosed with a chromosomal structural abnormality in the karyotype, to perform a PFT-SR on the embryos. In other words, it will be necessary to do IVF treatment and PG-SR analysis of the embryos before transferring them to avoid miscarriages or genetic abnormalities in future children.