In the practice of IVF, it is the general practice to limit the number of embryos transferred to the female in any given cycle to decrease the risk of multiple pregnancy. As a result, we may have more embryos that result from fertilization than can be transferred in a given cycle. In this situation, the couple may choose to cryopreserve (freeze) extra embryos with the intent of thawing and transferring them later. Cryopreservation provides a method to enhance to overall success of the initial assisted reproduction technology (ART) procedure.  Future ART cycles with cryopreserved embryos tend to be less expensive and less invasive that the initial IVF cycle, since the woman does not require ovarian stimulation or egg retrieval. Once frozen, the embryos may be stored for several years. However, not all embryos survive the freeze and thaw process and the live birth rate is lower with cryopreserved embryo transfer.