Potential PGD patients will have to undergo an IVF cycle including controlled hyper-stimulation, ovulation induction, oocyte aspiration and embryo transfer. This is done to enable the production of a viable number of embryos for testing, in vitro fertilization and culturing of embryos and the ability to biopsy the embryo at the correct stage of development.
When the embryos generated through the IVF cycle have reached the 6-8 cell stage, approximately day 3 of culture (fig. 1), the embryo is biopsied and a blastomere is removed using micro-manipulation techniques (fig. 2). This single blastomere is then analyzed for the specific condition or disease using either a process known as FISH (Fluorescent In Situ Hybridisation) (fig. 3) or PCR (Polymerase Chain Reaction).
Those embryos that are found to be normal, for the specific condition tested, are transferred back into the patient on day 5, while those embryos found to abnormal are discarded.
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Figure 1: An image of an 8 cell embryo at day 3 of embryo culture. |
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Figure 2: The removal of a single blastomere using micro-manipulation techniques. |
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Figure 3: An image of a blastomere stained with fluorescent probes using FISH. The single pair of each colour indicates the embryo is balanced for the specific chromosomes being tested. |
