Needs to be tightly regulated
- Frances A Flinter, senior lecturer in clinical genetics
- Centre for Preimplantation Genetic Diagnosis, Guy's and St Thomas's NHS Trust, London SE1 9RT
Pregnant women whose babies are at risk of having a genetic condition serious enough to warrant consideration of termination of pregnancy may be offered prenatal diagnostic tests such as amniocentesis and chorionic villus biopsy. For some couples, however, such tests are not acceptable, and preimplantation genetic diagnosis is an alternative.
Preimplantation genetic diagnosis involves testing the early embryo after in vitro fertilisation. One or two cells (blastomeres) are removed at biopsy from the preimplantation embryo at the 6–10 cell stage (day 3 of development), thus allowing replacement into the uterus of unaffected embryos.
Preimplantation genetic diagnosis can be offered for three major categories of disease. Firstly, it can be used to determine the sex of the embryo for sex linked disorders where the specific genetic defect at a molecular level is unknown, highly variable, or unsuitable for testing on single cells—for example Duchenne muscular dystrophy.1 Secondly, …