Preimplantation genetic testing (PGT) is a test that collects a small number of cells from an embryo to check for chromosomal (nst) abnormalities in the embryo. There are three types of test: PGT-A, PGT -M and PGT-SR.
The most common of these is PGT-A, which is a method of transplantation after confirmation of chromosome number. Because it helps increase implantation and pregnancy rates, and reduces miscarriage rates, this method is increasingly used in cases of multiple miscarriages in the past, resulting in repeated IVF failures and the number of miscarriages. The number of elderly infertile patients is increasing with the increase in late marriage.
Diagnosis of 46 chromosomes through NGS testing
At Cha Bundang Hospital, some cells are removed from blastocyst stage cells and NGS technology (Next Generation Sequencing) is applied to diagnose 46 chromosomes. It can be applied when parents have abnormalities in chromosome structure, when abnormalities in the number of chromosomes are suspected, during pregnancy the fetus has abnormalities in chromosomes in older women, recurrent spontaneous abortions, Repeated implantation failure and oligospermia.
Chromosomes in humans represent 2 cells linked together into a set (𝐧), the total number of normal cells is 46, including a total of 22 homologous chromosomes and a pair of sex chromosomes (XX, XY). . (2n=46) The numerical abnormality of chromosome 2n means that the total number of chromosomes in the embryo is not 46.
PGT test to ensure that the chromosome count is correct
Except for sex chromosomes, the chromosomes of normal embryos are numbered in pairs from 1 to 22. In most cases, if the number of chromosomes is abnormal, it is very difficult to have children. The goal of PGT is to check whether the number of chromosomes is correct and the typical diseases caused by abnormal numbers of chromosomes, including Down syndrome, Patau syndrome and Edwards syndrome.
In the case of abnormal embryos, implantation rates are very low and there is little evidence about the outcome of children born from abnormal embryos, so implantation is not recommended.
On the other hand, because blastocysts are very early embryos, the number of chromosomes between cells can be mixed between normal and abnormal. The condition of mixing normal and abnormal is called “mosaic”, in this case, after consulting with the treating doctor, decide whether to implant the embryo next to the normal embryo or not.
