Embryo freezing, also known as embryo cryopreservation, is a technique used in assisted reproductive technology (ART) to preserve embryos for future use. It is commonly employed during in vitro fertilization (IVF) treatment cycles when multiple embryos are produced but not all are transferred to the woman's uterus during the fresh cycle. Instead of discarding the surplus embryos, they can be cryopreserved for later use. The process involves carefully selecting high-quality embryos and then rapidly cooling them to very low temperatures using a technique called vitrification, which prevents ice crystal formation and preserves the viability of the embryos.

Embryo freezing offers several benefits, including the ability to preserve embryos for future IVF cycles, reducing the need for repeated ovarian stimulation and egg retrieval procedures, and providing flexibility in family planning. Frozen embryos can be stored for several years and thawed when the woman is ready to attempt pregnancy again, increasing the chances of a successful pregnancy without the need for additional ovarian stimulation or egg retrieval. Additionally, embryo freezing allows couples to undergo genetic testing on the embryos before transfer, enabling the selection of embryos with the highest chance of implantation and reducing the risk of genetic disorders in offspring.