11 - Cryopreservation of day two and day three embryos

Summary

Cryopreservation of human embryos is an important tool for in vitro fertilization (IVF) practice. Human embryos can be cryopreserved efficiently from the pronuclear to blastocyst stage. For day 2 or day 3 embryos, it is better practically to culture the thawed embryos further for a period of time before transfer in order to confirm that these embryos resume development. The selection method for post-thawed embryos for transfer directly affects the clinical outcome in terms of pregnancy and live birth rates. Two basic techniques have been employed for the cryopreservation of human embryos: slow freezing and vitrification. Slow freezing was used first and is still the most common method for cryopreservation of human embryos. Vitrification is a relatively new technique and has been introduced to cryopreserve human embryos in recent years. Many studies have reported improved success rates in terms of clinical pregnancy and live birth rates with the vitrification technique.