The cryopreservation procedure (i.e. freezing eggs) provides the staff the opportunity to reduce the number of embryos (fertilized eggs) initially replaced into the uterus in order to limit the risk of multiple gestations. The freezing of unused embryos also maintains their viability for future transfer should the fresh transfer be unsuccessful.
Cryopreservation reduces the number of fertility drug stimulations and subsequent oocyte retrievals required. During an egg retrieval, as many as 15 eggs may be harvested and fertilized. Since a maximum of two to six embryos are transferred, additional embryos are often remaining.
With cryopreservation these extra embryos can be saved for future transfer, decreasing the need for additional costly retrievals. It is important to note that not all unused embryos will be frozen for later use. Only those that appear to be of sufficient quality to survive the cryopreservation procedure will be chosen.