What Is Genetic Diagnosis (Pgd) Before Implantation in IVF?

Recent advances in genetics have enabled genetic studies to be carried out in embryos developed by IVF methods. This method is called “genetic diagnosis in embryo” or “preimplantation genetic diagnosis”. These processes are carried out by taking 1 or more cells from embryos that develop as a result of fertilization of egg cells with sperm cells in a laboratory environment.

By using special methods in the received cells, the diagnosis of numerical and structural chromosome disorders and single-gene diseases (such as thalassemia, sickle cell anemia, cystic fibrosis) of future infants that these embryos will develop can be made.

 Who is the PGT Test for?

Today, PGD can be performed in almost every case where the genetic mutation (disorder) causing the disease is known. However, diabetes, hypertension, some cardiovascular diseases, and cancers are currently excluded from this practice, which is considered to be genetically transmitted diseases but many genetic factors play a role in the formation of the disease.

Preimplantation Genetic Diagnosis (PGT)

Preimplantation genetics (PGT) is simply a genetic test of embryos before being transferred to the mother’s womb. PGT is recommended for couples at risk of having a genetic disease or anomaly to their children. Only healthy embryos are transferred to the mother’s uterus and healthy children are born.

In addition to preimplantation genetic diagnosis, preimplantation genetic screening (PGS) is the process of screening embryos for aneuploidies (numerical chromosomal disorders) in families with a healthy genetic structure.

Since only unaffected and healthy embryos are transferred, PGT and PGS stand out as an alternative to prenatal diagnostic techniques (amniocentesis or chorionic villus). When prenatal diagnosis gives negative results, it saves families from a difficult situation such as termination of pregnancy. PGT and PGS are currently available as the only precautionary measure to prevent the risk of giving birth to a child with a genetic anomaly or disease before implantation.

Even if couples with chromosomal or genetic diseases do not have problems such as infertility, they can have a healthy child thanks to IVF treatment and the application of PGT to developing embryos. This process works with the system of taking 1 or 2 tissue samples from the embryos formed by fertilization of the eggs taken from the mother with the sperm taken from the father during IVF treatment and placing the embryos determined to be healthy in the mother’s womb.

CONDITIONS REQUIRING GENETIC DIAGNOSIS IN TUBE BABY APPLICATIONS

Reproductive techniques are very important for couples who cannot have children due to infertility. Infertility can be either female or male. In terms of genetic reasons, the most common problem is chromosome disorders. Numerical disorder of sex chromosomes is detected in at least 5% of men who cannot have children. Another condition associated with low or no sperm count is the loss of genes responsible for sperm production on the Y chromosome. Although rare, more complex chromosome rearrangements, such as translocation, can also be detected in these individuals. For female patients, numerical chromosome disorders such as Turner Syndrome and rare structural chromosome disorders can be seen. Therefore, before starting IVF treatment, it is recommended that couples are directed to a genetic diagnosis center to get counseling and examine their chromosomes to exclude possible genetic causes or to determine the genetic cause if any.

In cases with genetic disease carrier:

• Chromosome Numerical Disorders (Karyotype Anomalies; Down Syndrome, Turner Syndrome, Klinefelter Syndrome, etc.).
• Structural anomalies (Reciprocal and Robertsonian Translocations).

• Single gene diseases (Thalassemia, cystic fibrosis, and Duchenne Muscular Dystrophy, etc.).

• X-linked diseases (linked to Sex chromosome).

Indications for Preimplantation Genetic Screening (PGS)

Most early pregnancy losses are associated with aneuploidy. Since only chromosomally normal embryos are transferred with the PGS procedure, a high rate of decrease in pregnancy losses during the 1st and 2nd trimester periods are observed. Currently, preimplantation genetic screening is widely used for the following indications:

• Advanced age of prospective mothers.
• Couples with a history of recurrent pregnancy loss.
• Couples who have repeated implantation failure

Advanced male infertility factor

The patient population seen above carries the risk of IVF failure due to the high rate of aneuploid embryos. PGS increases IVF success by providing a selection of embryos with higher chromosomally normal implantation chances.

PGS/PGT method Tubehow does it improve baby outcomes?

PGS / PGT is the most modern approach that allows the embryos to be scanned for all chromosomes (24 types; 46 units) and allows the detection of healthy embryos without damaging the embryos. With the transfer of a single embryo, which is found to be chromosomally normal, both the rate of conception increases and the risk of pregnancy loss is reduced in all age groups.

What are the advantages of PGS/PGD?

• By removing the best embryo to be transferred, increasing the chance of pregnancy, deciding on the embryo to be frozen or eliminated,
• To minimize the risk of miscarriage,
• To be able to guide patients better,
• Motivating patients with chromosomally normal embryos but who have not been able to provide pregnancy.

Some points you should be prepared with Preimplantation Genetic Diagnosis (PGD) method

• Some technical problems may arise during the preparation or biopsy phase.
• Even after a successful IVF and PGD procedure, pregnancy may not occur after the transfer.
• Since only a certain number of chromosomes can be controlled, not all chromosomal and genetic abnormalities can be diagnosed with PGD.

As a result, only a certain test can be performed on the biopsied cell. It is not possible to scan all genetic problems with a single cell taken for testing.

How is PGT Test Performed?

It is important for couples who think of PGT to have an idea about the genetic disease that may affect their children before making a decision, to understand their inheritance, and to get genetic counseling to detect the genetic problem causing the disease.

In the presence of genetic disease diagnosed in Preimplantation Genetic Diagnosis and known cause, a preparatory study called “setup” is performed by first taking blood from the spouse’s parents and spouses, if any, from the sick child or family member. Then, cellular material from early embryos is tested for the relevant genetic mutation (disorder). After diagnosis, only unaffected (intact) embryos are selected for transfer to the uterus.

After pregnancy occurs, it is recommended that the baby is also checked by an appropriate prenatal genetic diagnosis method (Cvs, amniocentesis, etc.).

We can perform genetic analysis with different techniques, and we perform chromosome analysis with the Next Generation Sequencing (NGS) method, which is the most reliable, the most reliable and up-to-date technique, and Artificial Intelligence (Artificial Intelligence Technology) for our patients. For genetic analysis, we cooperate with IGENOMIX Genetics Laboratory, which is the world giant in reproductive genetics, has more than 10 branches on different continents, and whose main center is Valencia-Spain.

PREIMPLANTATION GENETIC DIAGNOSIS – WHAT IS GENETIC DIAGNOSIS (PGS) IN EMBRYOS?

The process of performing genetic examinations in embryos created in a laboratory environment by applying assisted reproductive techniques is called ‘PGT- Preimplantation Genetic Diagnosis’. In another saying; “It is the process of defining the genetic diseases in the pre-pregnancy period, yet at the embryo stage. It means that the embryos developed in the laboratory environment take 1, 3, and 4-6 cells on the 5th day and define the numerical and structural chromosome disorders in these cells using different genetic techniques.

Also In addition to chromosome diseases, the diagnosis of single-gene diseases (such as thalassemia, sickle cell anemia, cystic fibrosis) can be made as well as DNA diseases. For numerical and structural disorders in chromosomes, a method called FISH was used up to 1-2 years ago and a limited number of chromosomes could be examined. In the years, all the chromosomes (24 chromosomes) could be examined by developing methods called aCGH, but initially, these chromosomes could only be examined numerically. Then, this system was developed and structural chromosome disorders were also examined. made available.

“SINGLE GENE DISEASE IS APPLIED TO THE WOMEN WHO HAVE A RISK” –

PGT test can be done for expectant mothers aged 35 and over, couples who did not have pregnancy despite two or more in vitro fertilization, couples with recurrent early pregnancy losses(miscarriages), balanced translocation carrier couples. It can be applied.

What is the difference between Preimplantation Genetic Diagnosis (PGT, PGD) and Preimplantation Genetic Screening (PGS)?

In the PGD method, apart from technical differences, a limited number of chromosomes can be evaluated, unlike genetic screening. For PGD, when embryos are in the 8-10 cell stage, 1 or 2 cells (blastomere) can be evaluated by staining (FISH) or PCR method, and up to 5-9 types of chromosomes can be evaluated. Apart from this, the PGD method is more preferred especially in the diagnosis of some single-gene diseases.

Genetic testing with PGT is performed long before – before the embryo implantation in the uterus, thereby avoiding “pregnancy testing” and possible abortion. Because many people PGTHe believes that it is more ethical and advantageous to destroy a few genetically abnormal daily embryos to prevent abortion during the advanced pregnancy or the elimination due to the disease in the child.

For a couple, the application of artificial insemination with PGT is an important effort and a high financial burden, since its costs are not currently covered by legal health insurance. Besides, PGT does not ensure the birth of the child desired to have artificial insemination.

If pregnancy occurs after PGT, the couple may assume that the genetic disorder that is most likely to be examined will not be hereditary. This is a great relief for the concerned couples.