PGD and “preimplantation” refers to the fact that the embryos are biopsied prior to placement into the uterus. This is known as a PGD blastomere biopsy and does not damage the embryo since it has not yet differentiated into different tissue types.
It is estimated that up to 60% of early pregnancy losses are due to genetic abnormalities, particularly aneuploidy (abnormal number of chromosomes). The success of PGD in improving IVF outcomes has been impaired by the fact that the embryo biopsy is performed on day 3 of embryo culture and then forty eight hours later the genetic analysis is obtained and embryo transfer is preformed on day 5.
PGD must be carried out in conjunction with IVF or ICSI. It consists of two main steps: an embryo biopsy (see below) and analysis of the biopsied cell by an independent laboratory.
Briefly, it is of relevance in any discussion of micromanipulation techniques to mention the potential to biopsy both eggs and embryos. This approach is known as preimplantation genetic diagnosis (PGD) and enables the screening of both the unfertilized egg by removal of the first polar body, or the fertilized multi-cellular embryo by removal of one or more cells either at the 6-12 cell stage or from the trophectoderm of the blastocyst. This material can be probed for either genetic mutations or gross chromosomal errors. This technology remains in its infancy and can be of profound importance clinically, but at this time only for cases with very clear medically-defined needs.
The biopsy procedure requires very exacting skills of the IVF laboratory, and the egg or embryo is not entirely free of risk during the procedure. Hence, couples whose offspring have a high chance of inheriting a genetic disorder may have their embryos screened. Women who are at risk of generating eggs with a high risk of chromosomal anomalies can benefit from having their eggs or embryos screened for chromosomal normality. While embryos can have their sex determined through this procedure, the FERTILITE team considers it inappropriate to do so except in cases of sex chromosome-linked disorders.