Genetics 101

Preimplantation Genetic Diagnosis (PGD)

Preimplantation genetics is a screening procedure that can be performed during an IVF cycle to identify embryos with chromosome abnormalities or those that contain markers for certain genetic disease and thereby avoid their selection for transfer. Cell/s are removed from the embryo for genetic testing in specialist laboratories.

PGD often is recommended for couples at high risk for producing offspring with genetic disorders, such as carriers of cystic fibrosis or Tay-Sach's disease. These couples may wish to prevent the birth of a child with an abnormal gene. In this case, special probes must be used in the test to detect the gene in question.

In IVF pregnancies of women 35 years or older, those with multiple failed IVF cycles and those with repeated miscarriages, research has shown that chromosomal abnormalities of the embryo increase either the risk of spontaneous miscarriage or the development of a genetically abnormal fetus. Screening the 9 chromosomes most involved in chromosomal abnormalities (chromosomes 13, 15, 16, 17, 18, 21, 22, X & Y) could prevent the initiation of these abnormal pregnancies in IVF patients. An estimated 60 percent of all early miscarriages are associated with a chromosomal abnormality in the embryo. The purpose of PGD is to select and transfer to the uterus only embryos that do not have numerical abnormalities for the 9 chromosomes tested in order to achieve higher implantation rates and fewer pregnancy losses.

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