PREIMPLANTATION GENETIC DIAGNOSIS (PGD): When one or both parent(s) are carriers of a genetic condition (gene mutation or unbalanced chromosomal rearrangement), a genetic diagnostic can be performed to determine whether that condition has been transmitted to the embryo. PREIMPLANTATION GENETIC SCREENING (PGS): 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.