HUMEDITロゴ

PGT-A



◆What is PGT-A?


Preimplantation genetic testing (PGT-A) examines fertilized eggs for chromosomal abnormalities after in vitro fertilization and selects fertilized eggs with no abnormalities for implantation into the uterus, This is a fertility test to prevent miscarriages due to abnormal chromosome counts.
In the early days, the FISH method was used, but it was limited and had a limited success rate. Later, the CGH method was introduced and it became possible to examine all 24 chromosomes using microarrays. More recently, NGS-based methods have been introduced to detect mosaicism in early embryos, and PGT-A, also called aneuploidy preimplantation genetic testing (PGS), screens 23 chromosome pairs and provides valuable information for IVF researchers.
The likelihood of aneuploidy increases with age as one of the most common causes of infertility treatment failure. Chromosomal abnormalities are the most common cause of infertility treatment, with the percentage increasing with age, reported in 60% of blastocysts at age 40 and over 80% at age 43. Transferring an embryo with chromosomal abnormalities can result in difficult implantation, miscarriage, or fetal developmental arrest, and patients undergoing fertility treatment are troubled by each of these situations.
HUMEDIT Corporation PGT-A Chart 01
Why limit the scope of PGT-A testing?" Citation. https://www.jsog.or.jp/activity/pdf/pgt-a_shiryo01.pdf

◆Advantages and Disadvantages


Advantages



Demerit




◆Method of Examination


①The embryo progresses to a blastocyst on the fifth day after fertilization.
②At the blastocyst stage, the blastocyst has divided into dozens of cells, some of which (3~5 cells) are extracted for DNA and chromosome testing.
③Since the embryos are growing during the test, they are cryopreserved to stop their growth, and the PGS results are used to identify normal blastocysts, which are then thawed and transferred.
Why limit the scope of PGT-A testing?" Citation. https://www.jsog.or.jp/activity/pdf/pgt-a_shiryo01.pdf


◆Notes

There is about a 10% chance of miscarriage for other reasons even if a PGS test is performed. Because the extra-nutritive cell test is performed on the part that will become the future "placenta," and the accuracy of the test is not 100%, false negative or false positive results may occur, and the percentage is estimated to be 0.5% to 1%. When transferring a chromosome positive embryo, the pregnancy rate is estimated to be about 70% and the miscarriage rate about 10%, noting that there is variability in pregnancy results regardless of the test.