Preimplantation Genetic Diagnosis is a process in which embryos developed outside of the womb are tested for particular genetic characteristics, usually genetic abnormalities that cause serious disease, before being transferred to a woman’s uterus. It is always performed within the context of in vitro fertilization (IVF) and has been available for testing since 1990.
PGD enables a variety of reproductive decisions. It permits doctors and prospective parents to select embryos for implantation that do not have a genetic abnormality associated with a specific disease, such as cystic fibrosis. It also enables doctors and parents to select embryos that possess a desired genetic trait, such as the sex of the unborn child.
According to J A. Robertson, PGD is ethically controversial because it involves the screening and likely destruction of embryos, and the selection of offspring on the basis of expected traits. This raises important concerns related to whether and when PGD should be used, its safety and effectiveness, and what it would mean to live in a society where one’s genetics become more a matter of choice than chance.
There are no legal limits on the use of genetic tests in PGD, therefore it has been used for both medical and non-medical purposes. Although PGD is primarily used to increase the chance of having a child free of a specific serious disease such as Mendelian disease or cystic fibrosis, it can also be used to select an embryo of a particular sex for non-health-related reasons.
For medical use of PGD, embryo screening for susceptibility and late onset conditions are logical extensions of screening for serious Mendelian diseases, and for “highly penetrant” adult disorders such as Alzheimer’s or Huntington’s disease, it prevents the birth of a child who will be healthy for many years, but who in his or her late 30s or early 40s will experience the...