◆What is PGT-A?

Preimplantation Genetic Testing for Aneuploidy (PGT-A) is a test in infertility treatment that examines chromosomal abnormalities in fertilized eggs after in vitro fertilization, selects embryos without abnormalities for uterine transplantation, and prevents miscarriages due to abnormalities in chromosome number.
Initially, the FISH method was used, but it had limitations and a limited success rate. Subsequently, the CGH method was introduced, allowing for the examination of all 24 chromosomes using microarrays. Recently, methods using NGS have also emerged, allowing for the detection of mosaic embryos in early-stage embryos. PGT-A is also called Preimplantation Genetic Screening (PGS), screening 23 pairs of chromosomes, providing valuable information to IVF researchers.
One of the causes of failure in infertility treatment is the increased possibility of aneuploidy with age. Chromosomal abnormalities are the most common cause of infertility treatment failure, with the percentage increasing with age, reported in over 60% of blastocysts at age 40 and over 80% at age 43.
Transplanting embryos with chromosomal abnormalities may lead to difficulties in implantation, miscarriage, and fetal growth arrest, causing patients undergoing infertility treatment to face individual concerns.
株式会社HUMEDIT PGT-A チャート01
"Why limit the scope of PGT-A testing?" Quoted from

◆Advantages and Disadvantages



◆Testing Method

① Progress to the blastocyst stage on the 5th day after fertilization.
② At the blastocyst stage, the embryo has divided into dozens of cells, and a few (3-5) of these cells are removed for DNA and chromosome testing.
③ During testing, embryo growth continues, so freezing is used to stop growth. Normal blastocysts are identified based on PGS results, thawed, and then transplanted.
株式会社HUMEDIT PGT-A チャート02 Quoted from "Why limit the scope of PGT-A testing?"

◆Points to Note

Even with PGS testing, there is still about a 10% chance of miscarriage for other reasons. Trophectoderm biopsy is a test of the part that will become the future "placenta," and because the test accuracy is not 100%, false negatives and false positives can occur, with a rate of about 0.5-1%. When transplanting euploid embryos, the pregnancy rate is about 70%, and the miscarriage rate is about 10%, and it should be noted that there is variability in pregnancy outcomes regardless of testing.