Embryo Freezing (Embryo Cryopreservation) involves freezing the eggs 2 to 5 days after fertilization during an IVF cycle with the goal of transferring the fertilized eggs (embryos) in the next 1-2 months (short term) or on a later date (long term) which is called Embryo Banking. In the short term, embryo freezing is used improve pregnancy rates from an In Vitro Fertilization (IVF) cycle. Common reasons for freezing embryos for the short term include high hormone (estradiol or progesterone) levels which can decrease pregnancy rates, unfavorable uterine environment (thin or abnormal uterine lining) or desire to perform Preimplantation Genetic Diagnosis (PGD) prior to transferring the embryos back to a patient’s uterus. Long-term embryo freezing (Embryo Banking) allows patient to become pregnant when the timing is better, for medical or personal reasons, or if they become pregnant during an IVF cycle and want to save extra embryos for a future pregnancy. Embryo Freezing can be used by patients or couples who would like to preserve their fertility for the future, and typically has higher pregnancy rates than Egg Freezing (Oocyte cryopreservation).