Preimplantation Genetic Diagnosis
Although the development of the first-trimester prenatal diagnosis has significantly improved the potential to avoid genetic diseases, selective abortion are still a major issue in the case of an affected fetus. Preimplantation genetic diagnosis (PGD) is used as an option to avoid the birth of an affected child without the need for selective abortion as an obligatory component within the prevention program. The below introduction describes these important developments addressing specifically the issues of PGD implementation within infertility treatments.
Presently, PGD is applied clinically in numerous IVF centers worldwide with a large number of unaffected children who are born after PGD in lots of clinical cycles performed for single gene and chromosomal disorders. Two methods of PGD are mainly used: polar body removal and embryo biopsy. It became possible due to the progress in micromanipulation and biopsy as well as in genetic analysis of single cells by PCR. Using both approaches has shown the sensible utility of preimplantation diagnosis of genetic and chromosomal disorders and the improvement in reliability and safety of the new technique in assisted reproduction.
The indications for PGD happen to be expanded beyond those used in prenatal diagnosis to include couples at high-risk of getting a newborn child with a genetic disorder (when confronted with antipathy toward elective abortion), poor prognosis IVF patients and couples at risk for producing offspring with late-onset genetic disorders, and preimplantation human leukocyte antigen (HLA) matching. Due to the high prevalence of chromosomal abnormalities at the beginning of pregnancy, the development of preimplantation cytogenetic analysis will not only make it possible to prevent the risk of age-related aneuploidies, but will also significantly improve embryo recovery and pregnancy outcome following PGD and should improve the effectiveness of IVF programs in general.
Introduction of microarray technology and new generation sequencing (NGS) for aneuploidy testing, which utilizes whole genome amplification as an initial step of the technique, also have the ability to do PGD for single gene disorders, with or without HLA typing in the same biopsy material. This method is increasingly used in PGD for single gene disorders and HLA typing in patients of advanced reproductive age.
Moreover, PGD may be used for nonmedical purposes (e.g. sex selection) for family balancing. Using PGD sex-selection aimed at avoiding “transgenerational transmission” of a disease might be allowed in some cases. Ukraine proscribes sex selection in PGD legally aside from sex-linked disorders.
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