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 stored in the laboratory for future use. Cryopreservation allows the patient to limit the number of embryos transferred “fresh” without discarding the unused embryos that could lead to a future 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.