Preimplantation genetic diagnosis

Preimplantation genetic diagnosis (PGD) is a technology that allows for the selection and transfer of embryos unaffected by genetic disease. The limited number of cells available for genetic testing is a weakness of PGD and has been solved by means of the development of various strategies such as polymerase chain reaction (PCR), fluorescence in situ hybridization (FISH) and cell recycling. A confounding factor in PGD is the existence of preimplantation embryos with severe chromosomal abnormalities. Therefore, genetic analysis should be performed with the assumption that embryos have severe chromosomal abnormalities. The visualization of metaphase plates allows screening for numerical chromosomal abnormality and several kinds of structural chromosomal abnormality. In addition, in vitro culture of single isolated blastomeres makes it possible to reexamine samples to ensure accuracy of the results and to obtain additional genetic information.