Pre genetic diagnosis, PGD, is done on the third day after egg retrieval, when the embryo typically has 8 cells. One cell from each healthy embryo is biopsied, and the chromosomal integrity of the cell is evaluated, reflecting the chromosomal integrity of the embryo. This is done for a number of different reasons. One reason why PGD is performed is to avoid having a baby with a genetic defect. Couples which carry a particular genetic defect can prevent passing on the genetic defect to their offspring. There are other reasons that PGD is performed. Your physician and IVF coordinator will discuss whether this is appropriate for you or not. There are other forms of testing the genetic integrity of the embryos. This includes procedures such as CGH, comparative genetic hybridization, where all 46 chromosomes are evaluated. There is a lot of technology which is available. Whether or not these procedures are appropriate for you is a very personal individualized discussion.