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Preimplantation Genetic Diagnosis (PGD)
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PGD is an advanced clinical laboratory technique, used in conjunction with in-vitro fertilization, which allows the physician and embryologist to screen for an abnormal number of chromosomes, and other genetic “defects,” which lead to genetic disease. PGD and “preimplantation” refers to the fact that the embryos are biopsied prior to placement into the uterus. This is known as a PGD blastomere biopsy and does not damage the embryo since it has not yet differentiated into different tissue types. It is estimated that up to 60% of early pregnancy losses are due to genetic abnormalities, particularly aneuploidy (abnormal number of chromosomes).
The success of PGD in improving IVF outcomes has been impaired by the fact that the embryo biopsy is performed on day 3 of embryo culture and then forty eight hours later the genetic analysis is obtained and embryo transfer is preformed on day 5.
The reality is that many chromosomally normal embryos may not survive to day 5 and do better if transferred on day 3. A second factor is that with the increase in the number of chromosomes being examined, there was a decrease in accuracy (more false-positives). Some of the embryos were characterized as abnormal when in fact they were normal.
In order to maximize the potential benefits of IVF and PGD while offering the patients the finest care, Dr. Allon and Dr. Dozortsev developed a unique concept termed, Same Day PGD™. Same Day PGD™ allows a vast majority of patients to take advantage of the PGD screening without the need for extended embryo culture, because embryo biopsy, FISH analysis, and embryo transfer all take place on day 3. To perform this biopsy, the Center for women’s medicine uses the most advanced FDA approved laser Zilos-tk. This innovative method allows us to transfer better quality embryos thus improving the chances of implantation and increasing pregnancy rates.
During this process, an in house genetic analysis of chromosomes X, Y, and chromosome 21 is made. This would satisfy the recommendation by the American College of Obstetrics and Gynecology (ACOG) of screening all mothers for Down Syndrome. Combined screening for 21, X and Y covers the vast majority of chromosomal aberrations seen in newborns within hours, while minimizing the rate of false-positive errors.
In cases where PGD is indicated due to one or both prospective parents caring known genetic mutations, we collaborate with Dr. Yury Verlinsky in Chicago and Dr. Mark Hughes in Detroit, world leaders in single gene disorders. PGD in these cases will be preformed on day 3; the embryo biopsied will be tested for up to twelve chromosomal aberrations as well as known translocations and single gene disorders. For these cases, the result will be obtained in 48 hours and the embryos will be transferred on day 5.
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