Preimplantation Genetic Diagnosis (PGD) is a relatively new diagnostic procedure that enables patients to pick embryos free of genetic defects. It was first performed in 1988 and since then, through the use of PGD screening and selection techniques in about thirty clinics worldwide, more than 2,000 children have been born free of genetic defects that were present in their family gene pool.

For couples at risk of having children with an inherited disease, PGD is a new alternative approach to preventing the birth of children with genetic disease. Traditional methods of prenatal diagnosis such as amniocentesis or chorion villus sampling (CVS) involve taking samples from an established pregnancy. If the fetus is diagnosed as affected, couples then have to decide whether or not to terminate the pregnancy. Some couples may have to undergo several terminations in their attempt to produce a healthy child. With PGD, In Vitro Fertilization (IVF) treatment is used to screen early embryos (within a few days of conception) for the genetic defect causing the disease. Couples can then choose to have only those embryos identified as free of genetic disease implanted in the woman's uterus in the hope that any resulting pregnancy be normal. Because it is a pre-pregnancy test, PGD offers patients a great advantage over both amniocentesis and CVS.