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Preimplantational genetic diagnosis (PGD)
It is a genetic analysis made on the embryos before implantation. It is a scientific advance that brings serendipity to the couples that, for any reasons, need to be sure that the health quality and the sex of their embryos. Genetic conditions as Down’s syndrome and Fragile-X syndrome can be avoided due this complex and safe procedure. The investigation is performed on embryos with at least 8 cells (third day of development). One or two cells (blastomeres) are removed for analysis- 25% of the embryo is removed with no impairment of development. The blastomeres are preserved for a cytogenetics evaluation as fluorescent in situ hybridization (FISH) for the identification of the different pairs of chromosomes or their fragments.
The PGD has the following therapeutic aims: determination and prevention of diseases linked to the X chromosome, such as hemophilia, Duchennes’ muscular dystrophy and fragile-X syndrome; determination of aneuploidies (wrong number of chromosomes) related to advanced maternal age. One of the most common aneuploidies is the trisomy of the 21st chromosome, the Down’s syndrome. Other genetic diseases, such as Tay-Sachs’ disease (common in Jewish families), falchion anemia, cystic fibrosis and more than hundred other diseases can be also determined.
