With recent advances in genetics, inherited disorders (e.g. -thalassemia, sickle cell anemia) affecting the hematopoietic and/or the immune system, can now be diagnosed at a molecular level. For couples who are carriers or affected by any of these conditions and are at high risk for transmitting it to their offspring, it is currently possible to detect the disorder during pregnancy. However the couples have the dilemma of whether or not to terminate the pregnancy if the genetic abnormality is present. In some cases this may also not be a viable option for religious or moral reasons. An alternative would then be to diagnose the condition in embryos before the pregnancy is established. Only the unaffected embryos would then be transferred to the uterus. This technique is referred to as Preimplantation Genetic Diagnosis (PGD). PGD is, presently, a valid alternative for families at a high risk for producing offspring with genetic disorders, such as thalassemia or sickle cell anemia, and to those who wish to avoid elective pregnancy termination or to prevent the birth of an affected child following prenatal diagnosis. PGD allows genetic analysis to be performed on early embryos prior to implantation and pregnancy. This provides couples at risk the opportunity to know that any pregnancy they achieve should be unaffected and obviates the need for screening during a pregnancy and hence prevent the physical and psychological trauma, and ethical-moral problems associated with possible termination. Technical advances in molecular genetics now enable physicians and scientists to be able to diagnose some inherited genetic or chromosomal disorders from a single cell of an early embryo. The information gained by PGD is used to select for replacement in the uterus only those embryos considered unlikely to be affected by the specific genetic disorder for which testing is performed. Couples who have PGD will undergo an in vitro fertilization (IVF) cycle for the purpose of creating embryos from the woman's eggs and man's sperm which will have genetic testing prior to replacement into the woman's uterus. The genetic material of the embryos (which is derived from both parents) is not altered in any way during a PGD cycle, and early embryological development is similar to natural conception, except that it occurs in the laboratory. Embryos that show normal development are biopsied with micromanipulation techniques to obtain sufficient cells (blastomeres) for analysis. The cells removed from each individual embryo are analyzed by genetic testing using PCR-based DNA amplification. Those embryos considered to be unaffected on the basis of this testing will then be available to be transferred into the woman's uterus. Preimplantation Genetic Diagnosis (PGD) of single gene disorders, combined with HLA matching, represents one of the most recent applications in reproductive medicine. This strategy has emerged as a tool for couples at risk of transmitting a genetic disease to select unaffected embryos of a Human Leukocyte Antigen (HLA) tissue type compatible with that of an existing affected child. At delivering, stem cells from the newborn umbilical cord blood can be used to treat the affected sibling.