PGD vs PGS - What Is The Difference?

When the question of genetic diagnosis arises, patients always have many questions about what it is, what algorithm is used for this procedure, and what information can be obtained as a result. In this article, we would like to provide you with complete information about the types of genetic testing and why it is performed.

What is the difference between PGD and PGS?

It should be noted that PGS and PGD are available to all patients undergoing IVF programs. Even if these two values sound the same, in the world of reproductive medicine they are still quite different. What these two types of testing have in common is that they allow embryos to be tested at the blastocyst stage and to identify possible chromosomal abnormalities. This type of testing provides us with information about whether the embryo is genetically healthy, reduces the risk of a negative pregnancy, and increases your chances of realizing the dream of becoming a parent. Below we provide you with more detailed information on these two types of testing.

What is PGD?

Preimplantation Genetic Diagnosis (PGD)- This type of testing is performed before the transfer of embryos to the uterus, even at the stage of their cultivation. PGD – is a type of genetic screening which detects the presence of genes for specific diseases. Usually, this test is recommended by doctors when patients (future parents) have detected abnormalities in the genetic plan (or in their family).

This genetic test for non-PGS allows you to check the embryo for one specific gene. In total, the embryo has more than 4,000 single genes that can be tested. We can identify a number of diseases that are most commons: Cystic Fibrosis, Huntington’s Disease, Tay Sach’s Hemophilia, Marfan’s Syndrome, Muscular Dystrophy, Spinal Muscular Atrophy, Beta-Thalassemia, Sickle Cell Anemia. Testing also helps identify possible genetic problems in the mixedgender of the embryo. Also, this test allows balancing the family.

What is PGS?

Preimplantation Genetic Screening (PGS)- This screening is performed at the same point as the PGD testing accordingly, on day 5 or 6 of the cultivation of embryos, their biopsy is performed and this sample is sent to a special laboratory. The waiting time for the result is approximately two weeks.

The main function of this genetic testing is to analyze all 46 chromosomes. Accordingly, the result of the study will be informed whether the embryo is aneuploid or euploid (recommended or not recommended for the implantation to the uterus). Aneuploidy could cause miscarriage, implantation failure, or chromosomal disorders like Turner or Down syndrome. The embryo with normal chromosomes is very important for normal implantation and development. PGS does not test for a specific disease. Down syndrome is caused by the presence of an extra chromosome 21 and Preimplantation Genetic Screening can determine that.

This test is usually recommended for patients undergoing insemination programs before the age of 35. Because from this time there is a fairly high risk of possible genetic abnormalities of the embryo. It also let’s you know the gender of the embryo for family balance.

PGD or PGS - which one is right for you?

Which testing to choose for yourself, and do you need it at all? It is worth consulting your doctor on this issue. It is also worth noting that not all couples who want to undergo insemination programs need such testing. After the procedure, doctors recommend that only healthy embryos be transferred to avoid possible genetic diseases in the future. Physicians may advise patients to perform this testing for embryos after previous tests on prospective parents. It can be karyotyping, FISH sperm testing, and others...

PGD and PGS testing are usually part of an in vitro fertilization program. Of course, PGD is a more comprehensive study and tests the embryo for one specific gene. We offer such embryo testing services at a cost from 2,000 to 3,000 euros.

It is also important to choose a certified clinic and laboratory to perform this test. Because it is a troublesome procedure performed with the embryo itself. Our embryologists conduct this testing very carefully and provide reports on the procedures performed.

What about success rates of PGD and PGS testing?

Our statistics according to the programs executed in recent years are as follows.

2016 2017 2018 2019 2020
Clinical pregnancy rates in Egg donation with Fresh donor’s oocytes. 61% 66% 63% 64% 65%
With PGD or PGS testing. 81% 86% 83% 84% 85%

Speaking about the statistics of the success of programs with PGS testing, we can without any hesitation add 20-25% of success in accordance with the implantation of embryos in the uterus, which results in a positive pregnancy. So, this additional testing, even if you do not have critical reasons for it, can dramatically increase your chances of a successful pregnancy.

Оbstetrician-gynecologist, reproductive specialist, doctor of ultrasound diagnostics

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