Some couples are fortunate enough to collect a large number of embryos from one egg collection. Any remaining viable embryos that are not transferred into the woman’s uterus during the month of treatment may be frozen (“cryopreserved”) in small tubes and kept in storage in the embryo laboratory for future use. This allows the patient to limit the number of embryos transferred “fresh” without sacrificing the chance that the unused embryos could lead to a pregnancy. The embryos may be kept in storage for several years. By transferring frozen-thawed embryos into the uterus, some patients have achieved 2-3 pregnancies in different years from just one egg collection.