What these terms mean
Preimplantation genetic testing describes laboratory procedures used with in vitro fertilization to examine cells from embryos before a pregnancy is established. The older term preimplantation genetic diagnosis (PGD) has often referred to testing for a specific inherited condition. Preimplantation genetic haplotyping (PGH) uses linked genetic markers to follow the inheritance of a gene region within a family.
Terminology and clinical practice have developed since this archive section was first prepared. Contemporary healthcare sources may use the broader abbreviation PGT and distinguish testing for particular genetic conditions, chromosome-number differences or chromosome rearrangements.
Why prospective parents may consider testing
Testing may be discussed when a family has a known risk of transmitting a serious inherited condition. Common starting points include:
- One or both prospective genetic parents have been identified as carrying a relevant genetic variant.
- A condition has appeared in the family and its genetic basis is known or can be tracked.
- Family ancestry is associated with a higher frequency of a particular inherited condition, although ancestry alone does not establish an individual diagnosis.
The process may help clinicians identify embryos believed less likely to be affected by the condition under review. Results are not a guarantee of pregnancy, birth or lifelong health, and the accuracy and limitations depend on the test and circumstances.
Why the subject is ethically contested
Embryos that are not selected may be stored, used under applicable consent arrangements or allowed to cease development, depending on law, clinical policy and the choices available. People who regard an embryo as having full moral status from fertilization may oppose testing that leads to non-selection. Others consider embryo selection ethically permissible when intended to reduce the likelihood of severe disease.
Disability advocates and other commentators may also question how screening affects social attitudes toward people living with genetic conditions. These concerns coexist with the reproductive choices, medical risks and family responsibilities considered by prospective parents.