Even if the parents have no known genetic abnormalities, their embryos can also be screened for chromosomal abnormalities to determine if the embryo has too many or too few chromosomes.
PGD has also been used for the purpose of gender selection
It can be used to detect which embryos are XX or XY. The desired embryos can be placed into the uterus to achieve pregnancy.
PGD is the only method for gender selection that is close to 100% accurate.
Preimplantation genetic testing is a test that is performed after the completion of IVF, when the eggs are fertilized and the embryos begin to divide.
A genetic test can be performed as soon as the embryo has reached the 8-cell stage (approximately on the 3rd day of development), by removing one cell (blastomere biopsy). Then the embryo returns to the incubator for further growth.
However, it is recommended to perform a biopsy as soon as the embryos turn into blastocysts (day 5-6). By the 5th day of development, the embryos will divide into about 100 cells and form the outer layer, which will eventually become the placenta. At this stage, a trophoblast biopsy can be performed by removing several cells from the outer layer. This procedure does not affect the quality of the embryo or its ability to implant.