Preimplantation genetic diagnosis

Preimplantation Genetic Diagnosis (PGD)

Preimplantation genetic diagnosis (PGD), pronounced /priːˌɪmplænˈteɪʃən dʒəˈnɛtɪk daɪəɡˈnəʊsɪs/, is a procedure used prior to implantation to help identify genetic defects within embryos. This serves to prevent certain genetic diseases or disorders from being passed on to the child. The term is derived from the Greek words "pre" meaning before, "implantation" referring to the process in which an embryo attaches itself to the wall of the womb, and "genetic diagnosis" referring to the detection of genetic abnormalities.

Procedure

The process begins with the normal procedures of In vitro fertilization (IVF) which includes egg retrieval and fertilization in a laboratory. Over the next three to five days, the embryos grow in the laboratory until they reach the blastocyst stage. At this point, a few cells are removed from each embryo through a procedure called embryo biopsy. The genetic material within these cells is then evaluated to determine if the embryos are free of genetic abnormalities. This information is used to select healthy embryos for implantation into the mother's womb.

Applications

PGD is used in conjunction with In vitro fertilization (IVF) to select embryos free of genetic diseases for transfer to the uterus. It is an option for couples who are at risk for passing on genetic diseases or disorders to their children. These may include:

Single gene disorders: Diseases such as Cystic fibrosis, Sickle cell disease, and Huntington's disease.
Chromosomal disorders: Conditions such as Down syndrome, Turner syndrome, and Klinefelter syndrome.
Sex-linked disorders: Diseases that are linked to the sex chromosomes, such as Hemophilia and Duchenne muscular dystrophy.

Risks and Considerations

While PGD can reduce the likelihood of passing on a genetic disorder, it cannot eliminate this risk completely. There is also a small risk that the biopsy procedure can harm the embryos. Furthermore, PGD does not replace the need for prenatal testing, such as amniocentesis or chorionic villus sampling (CVS).

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Preimplantation genetic diagnosis