For many years, freezing of embryos was performed using a “slow-freeze” method. Over the last decade, the technique of vitrification has replaced slow-freeze. The former process involves a rapid freeze method which is very important for oocyte (egg) freezing. Due to the high wáter content of oocytes, the slow freeze method cause crystals to form within the oocytes resulting in suboptimal outcomes.
Vitrification improves all outcomes with embryos and oocytes including survival percentage. Any freezing methods have the disadvantage of the risk of loosing embryos due to post thaw survival, storage tank failure, embryo tolerance for freezing due to patient age, related factor sor the skills of the Embryologist. Currently, there is no known disadvantage unique to the use of vitrification.