Preimplantation Genetic Diagnosis is used to test the genetic “makeup” of embryos during an In Vitro Fertilization cycle. Preimplantation Genetic Diagnosis (PGD) is useful for patients that are older than 35 years old, are concerned about birth defects, have a history of a genetic disorder in their family or are interested in family balancing. After the egg is fertilized in the lab, the fertilized egg (embryo) develops in the laboratory for 5 days. On the 5th day, several cells are removed from the embryo and the chromosomes or genes in the embryo are analyzed. Testing on the 5th day gives more accurate results and affects embryos less than traditional PGD testing which is done on the 3rd day. The fertilized eggs (embryos) are frozen (cryopreserved) while the genetic testing is performed so the results can be known prior to transferring the embryos to the patient’s uterus and the best embryos for transfer can be selected. The embryos are transferred to the patient’s uterus in the following 1-2 months, or on a later date depending on the patient’s reproductive plan.