PGS - genetic embryo screening - is it really worth it?
Preimplantation Genetic Screening (PGS) also known as Preimplantation Genetic Testing - Aneuploidies (PGT-A) refer exactly to the same thing, to the same technology. PGS is an embryo selection tool that can be used in infertility treatment. PGT-A is the newer nomenclature but both PGS and PGT-A are used interchangeably and refer to the exact same thing.
In IVF treatment without PGS you will very often have a number of embryos that you manage to form and you will need to make a decision about which embryo should be transferred. Whether you make that decision on day 3 after fertilisation or on day 5 (when you already have a blastocyst), the decision will be made on the basis of observational parameters. In other words, you will make a decision on the basis of how well does the embryo looked under the microscope. It is an observational basis to your decision.
In IVF treatment with PGS you make the decision on which embryos to transfer on the basis whether the embryo has got a normal make-up of chromosomes. You test the embryos to see if the embryos contain a normal complement of chromosomes and after you decided which embryos are genetically normal and which are not, you take the normally genetic embryos and you decide which one should go first according to the morphological grading. Morphological grading is a system by which embryos are ranked according to observational parameters (how well they look under the microscope).
What is aneuploidy/euploidy?
- Aneuploidy refers to an incorrect number of chromosomes in the embryo. If the embryo has an addition or deletion of a whole chromosome or a part of a chromosome than this embryo has aneuploidy.
- Euploidy is the correct and complete number of chromosomes with no deletions or additions of a whole chromosome or chromosome parts.
What are chromosomes?
The chromosomes are tiny packages of DNA found in every cell. In the normal human body, you should expect 46 chromosomes in total. In fact, the better way of describing this is to say that there are 23 pairs of chromosomes because we all receive one chromosome from our father and one chromosome from our mother - we, therefore, have 23 chromosomes from the paternal origin and 24 chromosomes from the maternal origin.
- Basics of IVF
- What is normal female/male karyotype and what is Down Syndrome (Trisomy 21), Edwards Syndrome (Trisomy 18), Patau's Syndrome (Trisomy 13) or Turner's syndrome?
- What is PGS / PGT-A?
- Why perform PGS and what is the correlation between embryo grading and euploidy?
- What are the possible advantages and disadvantages of PGS?
Dr Abramov talks about the above and more in the video below. If there is anything else that you would like to know about these topics or have any specific questions, please feel free to Contact Us.