Preimplantation genetic diagnosis (PGD) is a reproductive technology that allows couples at genetic risk to avoid the birth of affected offspring and to avoid facing prenatal genetic diagnosis and termination of pregnancy. Principally different from prenatal diagnosis, instead of preventing the birth of an affected child, preimplantation genetic diagnosis allows establishment of an unaffected embryo for the pregnancy from the onset and birth of an unaffected offspring. The detection and consequent avoidance of transfer of embryos with chromosomal abnormalities are also becoming an integral part of assisted reproductive technology (ART).