What are the differences between the different types of PGT: PGTA, PGT-M or PGTSR?

PGT-A
 
Preimplantation genetic testing for aneuploidy

With PGS or PGTA, we seek to know which embryos have a higher chance of becoming a healthy baby. During the course of In Vitro Fertilization, once an egg is fertilized and has become a blastocyst, our biologists obtain a small sample of the trophoblast, which is the group of outer cells that do not form part of the actual embryo, as they are destined to become the future placenta. While the embryo remains in the safe environment of the incubator, a specialized laboratory analyzes the 23 pairs of chromosomes using massive sequencing. We are checking for the presence of aneuploidies, which means additional chromosomes (trisomy) or missing chromosomes (monosomy). PGS or PGT-A is indicated in cases of advanced age, repeated miscarriages, implantation failures, or in cases of male factor with a possible genetic cause.

 
PGT-M
 
Preimplantation genetic testing for monogenic disorders

What we are looking for with this test is to delve into the possible mutations in the DNA that makes up each of the chromosomes. Genetic failures or anomalies can lead to serious diseases such as Beta thalassemia, cystic fibrosis, muscular dystrophy, hemophilia, among others.

 

PGT-M is indicated when we have family history that recommends its realization, and consists of:

  • A first evaluation by a doctor
  • Taking saliva or blood samples.
  • Biopsy of the trophoectoderm of each embryo.

Once the genetic analysis is performed by a specialized laboratory, it will indicate which embryos are suitable for transfer, thus minimizing the risk of transmitting a serious disease to the future baby.

 
PGT-SR
 
Preimplantation genetic testing for structural rearrangements

There are other types of DNA mutations called structural rearrangements. In these cases, we observe that a region of the chromosome itself is affected, either by a translocation, an inversion, a duplication, or a microdeletion. These rearrangements occur in 5% of individuals diagnosed with infertility. In a translocation, a fraction of the chromosome joins another different chromosome. It is called reciprocal when the segments are exchanged. In the case of duplication, a part of the chromosome has been copied during cell meiosis. A microdeletion is the opposite: a part of the chromosome is deleted. An inversion means that the chromosomal region exists but points in the opposite direction. These rearrangements can occur in both men and women, and of course in both at the same time, and they can lead to difficulties in embryonic development, implantation failures, and spontaneous abortions. The future baby could also develop numerous syndromes such as Down syndrome, Edwards syndrome, Patau syndrome, or have their intellectual or physical abilities affected. PGTSR is indicated when there are family history recommendations for its performance, and it consists of: - An initial evaluation by a doctor of both members of the couple - Collection of saliva or blood samples from both - Biopsy of the trophoblast of each embryo