ABSTRACT
Cryopreservation of human oocytes, embryos, or blastocysts allows us to maximize the potential for conception from any one in vitro fertilization cycle, and prevents wastage of embryos. Furthermore, this enables best utilization of a patient’s supernumerary oocytes after retrieval, and maximization of the use of embryos from a single stimulation cycle. In other words, at completion of a cycle a patient’s supernumerary embryos may be used beyond the fresh transfer, and can lead to later opportunities for pregnancy. Cryopreservation has been shown to increase pregnancy rates while allowing for further selection of embryos. In addition, it is possible to achieve implantation and pregnancy rates with frozen-thawed embryos close to those achieved with fresh embryos. Blastocysts have been shown to increase pregnancy rates while allowing for improved selection of potentially viable embryos. At this late stage of development lower numbers of embryos are transferred, resulting in fewer high-order multiple pregnancies and increased implantation rates. Decreased numbers of embryos are transferred which results in lower multiple implantations and the potential for more blastocysts to be placed in frozen storage with good potential postthaw, also this reduces the overall number of oocyte retrieval procedures to which patients are exposed. Blastocyst cryopreservation is
clearly an optimization of the assisted reproductive technologies (ART) process.
