Preimplantation genetic testing (PGT) involves screening the embryos for geneticdiseases and chromosomal disorders before they are transferred back into the womb in an IVF cycle. This procedure has an advantage of testing embryos before a pregnancy is established. PGT offers at-risk couples the opportunity to select embryos for transfer based on their geneticand chromosomal status. The goal of PGT is to identify abnormal embryos so they will not be transferred, leaving unaffected embryos to be selected for transfer that are more likely to make healthy, disease-free babies. Originally, PGT was developed in the late 1980s as an alternative for couples at risk of passing on serious geneticdiseases to their children. Instead of a prenatal diagnosis of a geneticdisorder with the possibility of terminating an affected foetus, the couple would use IVF to conceive, and the embryos would be tested before being transferred to the uterus for implantation. PGT M can identify the presence of chromosomal translocations (rearrangements of parts of chromosomes) and single-gene disorders (geneticdiseases that are the result of a single mutated gene). There are over 4,000 single-gene disorders. The most common diseases tested for are Thalassemia, sickle cell anaemia, Cystic Fibrosis, Tay Sachs, Fragile X, Myotonic Dystrophy. Our IVF units have successfully given pregnancies to thalassemia and sickle cell anaemia couples.
PGTa (Preimplantation GeneticScreening) is an advanced analysis for excluding abnormal embryos with the help of embryo biopsy and geneticanalysis. Embryos are screened for aneuploidy (missing or additional numbers of chromosomes), which is a leading cause of miscarriage and implantation failure (failure of the embryo to implant into the uterus). The goal of PGS is to identify chromosomally abnormal embryos, so they will not be transferred leaving the chromosomally normal embryos to be transferred in the attempt to achieve a successful pregnancy.
PGTa is thought to increase success rates for IVF in women over 35, as well as those who have suffered repeated IVF failure or recurrent miscarriage. While the older technique of performing PGS uses FISH analysis on a single cell, which is limited to analysis of 5 to 10 chromosome pairs out of the 23 pairs of chromosomes, newer testing methods such as single nucleotide polymorphism (SNP) analysis or comparative genomic hybridization (CGH) allow testing of all 23 pairs of chromosomes. In recent times Advanced techniques like NGS are used to find out and exclude abnormal embryos.
In this technique, the embryos can be tested without actually biopsying them. It’s a highly advanced technique where the geneticanalysis is done from the DNA which is retrieved from blastocyst culture media in which embryo is growing without touching the embryos. We are one of the few IVF groups in the world to have in house Non-Invasive Chromosomal screening in our Mumbai unit. We have done many PGTa patients using NICS in combination with NGS.
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