Genetic Factors in Success of IVF
Diagnosing Genetic Factors
The Role of Genetic Factors in IVF Success
It shows parallelism with ovarian aging and mitochondrial aging in women. Mitochondria are the organelles that provide energy to the egg cell. It provides the energy needed by the egg in the process of maturation and merging with the sperm and becoming an embryo. Low energy affects the genetic structure of the embryo negatively and affects the result of the treatment. In most of the structural abnormalities such as trisomy, monosomy and chromosomal breaks, the embryo is not accepted by the uterus or there are pregnancies resulting in miscarriage. The exceptions to this situation are Down syndrome (trisomy 21), Patau syndrome (trisomy 13), Edwards syndrome (trisomy 18), x and y chromosome anomalies. In this case, pregnancy continues, but it progresses with anomalies. This is a difficult process that the family and the attending physician do not want, and often the decision to terminate the pregnancy is made when it is detected. It is possible to detect all these negativities before embryo transfer by performing a pregenetic test (PGT).
What is pregenetic testing (PGT)?
PGD has been applied in IVF treatment since 1992, and it is a method for selecting embryos with normal chromosome number and genetically normal.
In the years when this method was first applied, the biopsy taken from the precursor cells that form the embryo, called blastomere, was examined in the 3rd day embryo. While analysis was performed with the Fish method, which was 5 chromosomes and an older method, today, more reliable and 23 pairs of chromosomes are examined and more reliable results are obtained with the NGS (Next generation sequencing) test.
While the PGT-A method determines whether the embryo has the correct number and sequence of chromosomes, PGT-M and PGT-SR methods are applied in cases of a known single gene disease or translocation carrier, respectively.
Who Is PGT Recommended For?
- advanced female age,
- severe male factor,
- recurrent pregnancy loss
- Recurrent IVF failure
- Translocation carrier
- History of single gene defect and/or need for HLA-matched transplant
- It can be applied to couples who want to shorten the time to live and healthy birth by choosing a genetically normal embryo.
Depending on the indication for PGD and factors such as the age and ovarian reserve of the person, it may be necessary to increase the number of embryos undergoing PGD with repetitive IVF applications. At this stage, the patients who need PGD to be performed on the embryos of the IVF doctor couple are carefully evaluated, and the treatment is planned after preparation with pre-treatment, if necessary, in the month when the most appropriate response will be obtained.
NGS (Next Generation Sequencing)
NGS (Next Generation Sequencing), also called next generation sequencing, is the newest and most comprehensive chromosome screening test that has started to be included in Preimplantation Genetic Screening (PGT) methods in IVF treatment as a technology used in chromosome screening in general. In 5th day embryos, PGD is evaluated with NGS, which is the most reliable test today.