How is the sample for PGD obtained?
PGD can be performed on two sample types – blastomeres and polar bodies. Approximately three days after fertilization an embryo contains approximately six to eight cells, also known as blastomeres. A specially trained embryologist microsurgically removes one blastomere, places it on a slide and sends it to a specialized laboratory for testing. The results usually take 24 to 48 hours, allowing a day-five or day-six transfer of the embryo into the uterus. Alternatively, a sample from the egg, before it is fertilized by the sperm and starts to divide, called the polar body can be sent for PGD. Polar body testing can be done earlier than blastomere testing, but is used only when the mother is the carrier of a chromosome translocation. The polar body is a small bit of cytoplasm that is extruded from the egg prior to fertilization. Its release is part of the normal development of the egg and it contains a complementary set of chromosomes similar to that present in the egg. Polar body results
