PGS stands for Preimplantation Genetic Screening. It's a process whereby a patient undergoes Invitro Fertilization. We can then take a biopsy of that embryo and send it off for evaluation. That biopsy can be done on day three of the embryo life where we take one cell, or on day five of the embryo life where we take multiple cells. That cell or cells are then sent off to a lab. Essentially, what we look at, are the number of chromosomes that are in that embryo. Theoretically, only transfer back the embryos that have a normal number of chromosomes. This can seem very attractive to patients as they are older because they know there is an increased risk of having chromosomal abnormalities. Unfortunately, the technique is still in its infancy. If you take a biopsy on day three of life, and you are only looking at one cell of an eight cell embryo; that one cell may not be representative of the rest of the embryo. Therefore, you might end up not transferring an embryo that would have been normal or putting back and embryo that might not be normal. It is not 100 percent accurate. We are now moving more toward doing a biopsy on day five of life, and taking multiple cells. We do think, in doing this, the accuracy is going to be better. When we are routinely doing the biopsies at this stage, this is probably going to be a technique in the future, that we are only putting back embryos that are chromosomally normal, back into patients.