Preimplantation genetic diagnosis: prevention of serious genetic disorders.

Couples who are at high risk of passing a severe debilitating genetic disorder on to their offspring now have an option for preventing their future child from being affected by the disorder. The new field in medical genetics, preimplantation genetic diagnosis (PGD), involves testing single cells biopsied from in-vitro derived preimplantation stage (approximately 8-cell) preembryos and assessing each of them as to whether it is affected or not. Thus, PGD dramatically reduces the risk of a couple having a child afflicted with a genetic disorder by diagnosing an affected preembryo before it is transferred to the mother for implantation and establishment of pregnancy. This preventive procedure allows parents who are known carriers of a severe genetic disease to have unaffected children.