Global Health Asia-Pacific Issue 2 | 2023 | Page 86



What is PGT-A ? PGT-A stands for Pre-implantation Genetic Testing for Aneuploidy . As its name suggests , it is a genetic test performed on your embryos before their implantation . This test allows for the screening of aneuploidies or an abnormal number of chromosomes , which may cause implantation failure and miscarriage . Aneuploidy may also lead to various chromosomal disorders such as Down ’ s syndrome and Turner syndrome .
How is the test performed ? Routine IVF cycle is performed and the subsequent embryos are cultured to the blastocyst stage ( Day 5 & 6 ), at which point several cells are biopsied from the blastocyst . These cells are sent for genetic testing while the blastocyst is cryopreserved for later use .
loss of the embryo ’ s cell number , compared with 3 % at the blastocyst stage . An additional advantage of blastocyst biopsy is the additional genetic material for testing ( 3-6 cells vs 1 cell ), which would entail a more accurate genetic result for the embryo . As such , a majority of IVF centres have moved towards blastocyst biopsies for PGT-A testing , where the risk of harming the embryo is minimal .
Is PGT-A for me ? The percentage of abnormal embryos increases with maternal age , and to a lesser degree , paternal age . This is especially true for women above 35 , in which the rate of attaining abnormal embryos increases dramatically . Furthermore , P�T-A will benefit couples who have had recurrent miscarriages or implantation failure . As aneuploid blastocysts that will cause adverse outcomes in pregnancies are deselected , even if you do not fall in the above groups , PGT-A will allow you to have a higher chance at a pregnancy and a shorter time-to-pregnancy .
Figure 1 . Embryo development
Is biopsy harmful to my blastocyst ? When the biopsy process is carried out on the blastocyst which has roughly 100-200 cells , the risk to the blastocyst is minimal , as only a few cells are removed during the process ( normally 3-6 cells ). In the past , biopsies were performed on Day 3 embryos , which would typically have 8 cells . As expected , the success rates then were lower , as by removing even one cell from the 8-cell embryo would entail a 12.5 %
Figure 2 . Increased percentage of abnormal embryos as maternal age increases
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