Preimplantation Genetic Screening and Diagnosis Using Fluorescent In Situ Hybridization (FISH)

Preimplantation Genetic Diagnosis (PGD) is the screening of embryos at the cleavage stage in order to select and transfer only the desired embryo. The main indications of PGD are monogenic disorders and aneuploidy. Additionally, PGD can be employed to distinguish a male from a female embryo or to choose a HLA-matched embryo to a child requiring bone marrow or cord blood transplant. The European Society of Human Reproduction and Embryology classifies PGD into two categories (Hum Reprod 24: 1786–810, 2009): high-risk PGD for patients at high risk of transmitting a genetic or chromosomal abnormality to their children, which includes single gene defects, namely autosomal recessive, autosomal dominant, and X-linked disorders, as well as chromosomal abnormalities (translocations, small deletions, etc.); and low-risk PGD (or PGS for Preimplantation Genetic Screening) for sex selection, and for infertile patients undergoing IVF with the aim of increasing the IVF pregnancy rates. Patients that fall into this category are those of advanced maternal age and repeated IVF failure and couples with normal karyotypes who have experienced repeated miscarriages.