Detecting the embryo with maximum implantation possibilities has always been the basis of many research projects in order to significantly increase pregnancy rates. Technological improvements and new scientific advances have allowed us to have a series of tools that, applied correctly and in a personalized way to our patients, can significantly increase the pregnancy rate compared to the expected rate. Even in those patients with chromosomal alterations or genetic diseases, it is possible to achieve pregnancies and births of healthy boys and girls free of diseases.
How good embryonic selection can increase pregnancy rates? These are the resources that we have in the IVF laboratory to detect the best embryos:
Time-lapse technology
Today embryo incubators with time-lapse technology allow direct monitoring from the moment of fertilization to embryo transfer and / or cryopreservation. Extensive data collection from all development enables the generation of algorithms that can predict which of the embryos has the highest probability of implantation.
Our experience certifies the usefulness of this incubator system in general, since they also maintain stable culture conditions throughout the embryo culture.
Blastocyst culture (5th day of development)
Another complementary selection mechanism, together with time-lapse technology, is the prolonged cultivation of the embryos. Currently the embryonic culture media allow culture until the fifth or sixth day of development where we already speak of embryos with a number of cells of between 80 and 100 and called blastocysts. This long culture is itself an embryonic selection system and it is important to note the high implantation power of blastocysts.
Scheduling a culture to the blastocyst stage can be an important screening tool, especially in those patients who have few embryos but are of good quality. Long culture can also be indicated to avoid multiple gestations, although it is very important to have an adequate number of embryos for the selection process.
PGT-A (Preimplantation Genetic Testing for Aneuploidy)
Another embryo selection technique consists of screening those embryos with chromosomal abnormalities (aneuploids) that may explain the low gestation rates in elderly patients, patients with repeated abortions or with repeated implantation failure. In these cases, the application of the chromosomal study called PGT-A allows us to select those embryos without chromosomal alterations (euploids) and, therefore, may have a higher probability of gestation.
The PGT-A uses «Next Generation Sequencing» (NGS) technology and it is important to highlight that the best results are always associated with the availability of a high number of embryos in the blastocyst stage. It is probably not advisable to indicate PGT-A in patients with a suboptimal response to IVF treatment.
PGT-M / PGT-SR (Preimplantation Genetic Testing for Mongenic diseases / structural Reorganization)
A significant percentage of our patients do not have sterility problems but are at high risk of transmitting a genetic disease or chromosomal alteration to their offspring. In these cases, the application of PGT-M or PGT-SR in IVF treatment allows the selection of embryos from healthy embryos, always complying with the strict legality established within the Assisted Human Reproduction law of 2006.
In general, then, the combination of all these techniques allows us to give individualized treatment according to the circumstances of our patients and offer a wide range of possibilities to achieve the desired pregnancy and overcome initial difficulties.
Josep Mª Calafell. Embryologist specialized in IVF assisted reproduction.
