Equipped with a special microscope, this technique makes it possible to extract one or more cells from the blastocyst-stage embryo and perform chromosome and genetic studies with the aim of identifying errors, for example, in the number of chromosomes leading to Down Syndrome, and others that cause embryo death.
Abnormalities in specific genes, leading to diseases, most of them inherited such as cystic fibrosis, can also be identified. Genetic Testing thus allows to select healthy from disease-bearing embryos.
With the current technology, it is not possible to ensure that the person will be born free from genetic disorders. Today, it is possible to perform chromosome and genetic tests in blastocyst-stage embryos (5th or 6th day of development); which is referred to as PGT (preimplantation genetic testing). For this purpose, approximately five cells are removed from the cellular group which will generate the placenta. This can also be achieved drawing some fluid sample from the blastocyst’s internal cavity. Once blastocyst biopsy is performed, the blastocyst is frozen, waiting for the chromosome/genetic study, which takes approximately 15 days. Once normal embryos are identified from disease-bearing ones, the woman can take a therapeutic decision. Chromosome studies aim at evaluating aneuploidies, PGT(a); this is, a disorder in number of chromosomes. This is the case of Down Syndrome, in which the embryo has a chromosome # 21 in excess, or Turner syndrome, in which one sexual chromosome (X), is lacking. These studies can also detect chromosome structure disorders, PGT(sr), (translocations and inversions), which are often associated to repetitive miscarriage. They can also detect disorders in specific genes, PGT(m), which are transmitted from mothers and fathers to children, and give rise to family diseases such as cystic fibrosis, thalassemia, spinal muscular atrophy, etc.
In Latin America, the use of PGT increases every year, as can be seen in Figure 22.
Figure 22. Proportion of initiated cycles, with pre implantation genetic testing (PGT) in embryos, by year and woman’s age. Latin America, 2016-2020.
As it can be seen in Figure 23, delivery rate significantly increases when embryos studied by PGT are transferred. In addition, the miscarriage rate significantly decreases. In fact, when PGT is performed and there are no normal embryos, there is no embryo transfer. In this way, the group of women studied by PGT are only included when chromosomic normal embryos have been generated.
Figure 23. PGT effect in delivery and miscarriage rates. Latin America, 2020.
The Latin American Registry of Assisted Reproduction (RLA) thanks the 204 institutions accredited by REDLARA which, every year, report their data to RLA.
This voluntary and rigorous contribution makes it possible to generate a powerful database, which helps doctors and patients take decisions based on the best existing regional evidence.
This educational portal is the result of a collaborative activity between the Latin American Network of Assisted Reproduction (REDLARA), and University Diego Portales from Chile, which allow the link between the reproductive science and technology advances with the needs of people suffering from infertility and other forms of reproductive impairments.
We thank Dr. Ariel Ahumanda and Dr. Gustavo Martínez from Argentina for: images and videos of spontaneous in vitro fertilization, ICSI and PGT,
Dr. Roger Molinas from Paraguay for: videos of follicular aspiration and embryo transfer,
Dr. Javier Crosby from Chile for: images of different stages of in vitro embryo development,
Dr. Yasuyuki Mio from Japan for his video of in vitro embryo development.
We especially thank the industry for providing the financial support, which is so necessary to keep the Latin American registry as a pillar of this international cooperation, which today includes 16 countries and more than 200 collaborative institutions, from Mexico in the north to Chile in the far south.
