Preimplantation genetic testing (PGT) is an early form of prenatal genetic diagnosis where abnormal embryos are identified, thereby allowing transfer of genetically normal embryos.
PGT is basically a type of assisted reproductive technology (ART) used to assess the genetic makeup of embryos produced through in vitro fertilization (IVF). PGT helps to identify embryos that are most likely to result in a successful pregnancy and a healthy baby. By detecting chromosomal abnormalities or genetic disorders, PGT can significantly increase the chances of a successful pregnancy and reduce the risk of miscarriages. It is commonly used by couples who have a known genetic disorder in the family or who have had multiple failed IVF cycles.
Some patients seek IVF with PGT to reduce the chance of a specific genetic condition occurring in their children. This type of PGT is called preimplantation genetic testing for monogenic disorders (PGT-M). In some cases, the patient themselves may have a genetic condition such as neurofibromatosis type 1 or Marfan syndrome that could be passed on to their children. In other cases, both members of a couple may be carriers for a recessive genetic condition such as cystic fibrosis or sickle cell anemia, or the individual using their eggs may be a carrier for an X-linked condition such as Fragile X syndrome. HLA matching is also available for families with certain blood disorders who may wish for an embryo that could be an HLA match for a sibling or other family member.
The woman will need to undergo an IVF cycle to retrieve eggs and create embryos. The embryos are then monitored in the laboratory until day 5 or 6 after fertilization when they are referred to as blastocysts. At that point, a small number of cells are removed from each embryo and shipped to an outside laboratory for PGT.
While PGT is being performed on the DNA from the cells that were removed, the embryos are cryopreserved (frozen) and stored in the laboratory. Once the PGT results are available, typically in 1-2 weeks after the biopsy, the patient will be notified of the results. If the embryos are appropriate for transfer, the doctor will schedule a frozen embryo transfer.
PGT-A and PGT-SR
This type of genetic testing can also evaluate an embryo’s chromosomes, the structures in every cell that contain our genes. It is not uncommon for embryos to have random chromosome abnormalities such as missing or extra chromosomes, also known as aneuploidy. Embryos with aneuploidy are more likely to result in a miscarriage or failed IVF cycle. Less commonly, aneuploidy may result in the birth of a child with a chromosome condition such as Down syndrome (trisomy 21).
For those specific cases doctors suggest preimplantation genetic testing for aneuploidy (PGT-A) that provides additional information about the reproductive potential of the embryos and may help select the best embryo for transfer. PGT-A is most often considered for patients who have had recurrent pregnancy losses (miscarriages), multiple unexplained failed IVF cycles, a prior pregnancy or child with certain chromosome abnormalities, or based on the age of the individual providing their eggs.
The cost effectiveness of PGT-A is difficult to quantify because of the intangible costs of failed implantation and spontaneous loss, as well as variability in treatment costs. In addition, it may prove to be a factor in decreasing the multiple gestation associated with IVF because of the current recommendation of single euploid embryo transfer regardless of age. In any case, doing this type of genetic testing -along with the classic PGT and PGT-SR- is not an easy decision, and you should carefully consult with your fertility specialist in order to determine the right steps of action.
The final type of PGT is called PGT-SR and is for structural rearrangements. This type of PGT is performed when a patient or their partner has a rearrangement of their own chromosomes such as a translocation or inversion. A person with a structural rearrangement of their own chromosomes is at increased risk to produce embryos with missing or extra pieces of chromosomes. Embryos with missing or extra pieces of chromosomes are more likely to result in a miscarriage or a child with serious health issues. PGT-SR can help to reduce those risks.
In fact, approximately 50% of first trimester miscarriages are due to a chromosome abnormality in the fetus. Chromosomes are the inherited structures in the cells of our bodies. A baby has two copies of every chromosome — one inherited from the mother in the egg, and the other inherited from the father in the sperm. Once a couple has had a pregnancy affected by a chromosome abnormality, there is a slightly greater chance for their future pregnancies to be affected with chromosome abnormalities. In some cases prenatal diagnosis, such as chorionic villus sampling (CVS) or amniocentesis, are offered in future pregnancies. CVS is a prenatal test that involves taking a sample of tissue from the placenta to test for chromosomal abnormalities and certain other genetic problems.
So, while we established that PGT goes hand by hand with IVF, it is time to justify why Greece is considered one of the top fertility destinations, especially for IVF. As of May 2022 the country raised the IVF age limit from 52 to 54 years, giving to even more women the ability to perform the treatment and achieve the goal of pregnancy. Also, by having more that 50 fertility clinics with state of the art technology, highly experienced doctors, lower prices that other European countries, and no waiting lists, for many it is considered one of the best countries to start their fertility journey.
No one can deny that the things you should consider while trying to conceive might be overwhelming. All those tests, exams, and possibilities of something going wrong, would definitely add up to the stress you might already experience. What you need to do is to trust your doctor and have the ability to talk to him/her openly about your concerns. If you also need a space to talk to, and share your experiences finding comfort in others that may experience the same, follow us on our Facebook group “Your fertility journey by MEDIPASS”.
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