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What does PGD and PGS mean
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What does PGD and PGS mean?
PGD is an abbreviation of Preimplantational Genetic Diagnosis, and consists in apply different genetic studies in embryos prior to implantation. These studies are usually linked to an IVF cycle, and could be referred to different levels.
First level is known as PGS (preimplantation genetic screening), formerly PGT-A or preimplantation genetic testing for aneuploidies. At this level, the studies are centered in the detection of "aneuploidies", differences on the chromosomic dotation on the embryos. Embryos could be carriers of different chromosomic alterations, produced during gamete development. The presence of aneuploidies in embryos is common, and their numbers increase with parental age.
On the other hand, those couples with the presence of balanced translocation are could take profit for these techniques, selecting those embryos without unbalanced translocations, and increasing the pregnancy chances.
In both cases, the PGT-A technique includes the determination of the chromosomal status of IVF embryos by screening all 23 pairs of human chromosomes, and only those with exactly two copies in each chromosome will be selected as “transferable”. Embryos with aneuploidies cannot implant and/or are the cause of fetal miscarriage.
We recommended the use of ReproSeq™ PGS kits from ThermoFisher Scientific to help in your PGT-A studies.
PGT-A techniques can be applied to all patients, especially those with advanced maternal or paternal age, with previous repeated miscarriages, etc.
Second level, more specific, is known as PGT-M from "monogenic" disease study. This technique is applied during in-vitro fertilization processes to ensure that we choose those embryos that not received a specific allele, a genetic defect or a mutation presented in their parents. After this genetic study, the embryos marked as are non-carrier of the alteration will be able to be transferred to a mothers' womb.
This technique is specially designed for these couples that are carriers of a genetic disease (usually from familiar origin) and desire have descendants without risk for suffering this. For example, couples that are carrying CFTR mutations (recessive) or those with predisposition to suffer Huntington disease (on the HTT gene). Also, we could apply these techniques for other studies, as HLA typing.
For PGT-M studies we offer our PGD-SEQ kits. Each of them is specially designed to test a specific disease (and it is also possible to design a specific panel over demand). Please feel free to consult our test available.
PGT-M techniques can be applied for those patients under risk of transferring genetic diseases to their descendants, usually from a familiar origin.
All these techniques are considered for experimental use, and should be applied according local laws.