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| Resources > Newsletters > Preimplantation Genetic Diagnosis (PGD) |
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Preimplantation Genetic Diagnosis (PGD):
A Technique Whose Time Has Arrived |
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| Preimplantation Genetic Diagnosis (PGD) provides reproductive specialists with a powerful tool in the treatment of infertility. Initially developed to prevent the transmission of genetic disease, PGD has established its role in the day-to-day therapeutic approach to the infertile couple and couples with recurrent pregnancy loss. |
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| PGD refers to detecting genetic information through the isolation and analysis of individual cells (blastomeres) from a developing embryo. In its earliest development, PGD required the amplification of DNA in order to detect single gene disorders, such as Cystic Fibrosis and Tay Sachs Disease. This technique is still used for couples at risk for such conditions. A far more common technique used with PGD is Fluorescent In Situ Hybridization (FISH). FISH facilitates the identifi-cation of chromosomal abnormalities such as aneuploidy (incorrect number of chromosomes), mutations, deletions, trans-locations and inversions, all of which can predict developmental problems in the embryo and fetus that lead to recurrent pregnancy loss. |
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Trisomy 21
Blastomere analysis using FISH can demonstrate aneuploidy.
The red fluorescent dots are markers for chromosome 21.
The green fluorescent dots are markers for chromosome 18. |
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| PGD procedures require the removal of a blastomere from the embryo on the third day after in vitro fertilization. Single gene disorders can be detected and therefore prevented, making it possible for couples or individuals with serious inherited disorders to build their families without the risk of transmitting those disorders to |
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| their children. Below is a partial listing of conditions for which this technique has been successfully applied: |
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| Cystic fibrosis |
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Myotonic dystrophy |
| Fragile X syndrome |
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Beta thalassemia |
| Tay-Sachs disease |
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Sickle cell disease |
| Huntington’s disease |
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Spinal muscular |
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| The FISH technique of blastomere analysis differs from single gene detection in that, with FISH, the intact nucleus from each cell is examined. Current technology allows multiple chromosomes to be visualized within approximately four hours, while a second, additional set can be viewed later, totaling up to ten chromosomes. FISH pro-vides specific information about chromosomal number, i.e. it can detect aneuploidy of the observed chromosomes. This information is used in order to select only normal, euploidic embryos for transfer to the uterus. Transfer is generally done at the blastocyst stage. One of the more common indications for PGD is in the management of recurrent pregnancy loss (RPL) due to parental chromosomal ab-normalities. More recently, it has been advocated for the manage-ment of couples who repeatedly fail to conceive with IVF. |
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| MATERNAL AGE GROUP: |
< 35 |
≥ 35 |
Total |
| No Subjects: |
21 |
37 |
58 |
| BEFORE PGD: |
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| Previous number of pregnancies: |
96 |
205 |
301 |
| % Previous lost pregnancies: |
90% a |
86% b |
87% c |
| Expected loss in next pregnancy d : |
29% |
45% e |
37% f |
| AFTER PGD: |
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| Pregnancy rate per retrieval: |
52% |
39% |
43% |
| Pregnancy loss rate: |
23% a |
12% e,b |
17% f,c |
| Take home baby rate / retrieval: |
40% |
34% |
36% |
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| a,b,c p<0.001 e p=0.004, f p=0.028, Munne et al.., 2005 Fertil Steril, in press |
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| At GENESIS, we use PGD in order to screen for single gene disorders and also for aneuploidy detection to reduce the risk of recurrent pregnancy loss. Our Laboratory Director, Michael Lee, MS, ELD, is an expert in PGD. He has performed over 200 procedures as a consultant to many reproductive laboratories around the nation. |
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| August 2005 |
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