Genetics

Preimplantation genetic diagnosis (PGD) involves producing fertilized oocytes in vitro, which are then cultured until they reach the 8-cell blastomere stage. A single cell is removed from the embryo and tested for a specific genetic disease or chromosome abnormality. The embryos that have negative results for the disease are transferred to the woman’s uterus. If the embryo implants and becomes a viable pregnancy, it is expected to be unaffected by the tested disease.

Bottom line. A couple who wishes to avoid both prenatal testing and making decisions about terminating an affected pregnancy but who also wishes to avoid having a child with a specific genetic disease might be interested in PGD; they should receive genetic counseling beforehand. Patients are responsible for covering the substantial costs of the in vitro fertilization and PGD procedures, and they should be aware of the possible need for multiple cycles and the pregnancy success rate of 30% to 45%.

The complete Gene Messenger—Preimplantation Genetic Diagnosis by the GenetiKit research team is available on CFPlus.* Past Gene Messenger articles can be accessed online at www.cfp.ca. On the home page, click on Collections in the left-hand menu, then click on Genetics.

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