PGD is employed in conjunction with in vitro fertilization. Couples want to know the sex of their embryos before they are transferred into the mother’s uterus, for various reasons. They may want to be sure that only the embryos of the desired sex are transferred to the mother, or if a couple has a high risk of transmitting a genetic disease, they may want to make sure they are excluding embryos that have abnormal chromosomes.

PGD enables the embryologist to biopsy the embryo and determine if a disease is present prior to selecting the embryo for transfer to the mother.

Every cell in the embryo contains a copy of the genetic makeup of the entire person. PGD begins with an embryo biopsy. A small hole is made in the egg membrane (zona pellucida) when the embryo has grown to 6-8 cells.

One cell is removed from the embryo so that the chromosomes can be examined. Removal of one of these cells does not harm the developing embryo.