PGD is an early form of prenatal diagnosis, it is often undertaken on fertile patients to avoid antenatal diagnosis. It is also performed on infertile patients to improve their chances of success. An additional tool that is used with PGD is called Flourescent In Situ Hybridization (FISH). This helps sexing the embryos and ruling out chromosomal abnormalities on chromosome 11, 13, 18, 21, X and Y. Knowing the sex of the embryos helps to exclude disorders linked to the sex of the child. There are only 100 PGD centres world-wide, we are one of them.