Preimplantation Genetic Diagnosis
Preimplantation Genetic Diagnosis or PGD is a method that enables testing genetic disorders in embryos before embryo transfer. To achieve this, one to few cells are removed from the embryos either third or fifth day of development via a microscopic procedure in the embryology lab. These cells then are subjected to genetic analysis, normal embryos are selected and transferred by day 5 or 6 of the development. Common indications of PGD include testing chromosome numbers (aneuploidy screening), testing for single gene disorders (e.g. sickle cell disease, Fanconi’s anemia, cystic fibrosis, BRCA mutations, Retinoblastoma gene, others), conceiving an HLA-matched sibling for bone marrow transplantation, chromosome translocations, gender preference (due to sex-linked disorders or family balancing). We have diagnosed many genetic conditions with PGD but new diseases are continuously added to the list. As long as the genetic mutation or genes related in transmission are known, a diagnostic strategy can be developed. However for rare disorders, probe preparation can take weeks to months and hence advance planning is important.