Evolution of human oocyte cryopreservation: slow freezing versus vitrification

Area of Science:

• Reproductive Medicine
• Cryobiology
• In Vitro Fertilization (IVF)

Background:

• Oocyte cryopreservation is a key technique in assisted reproductive technology (ART).
• Comparing slow freezing and vitrification methods is crucial for optimizing fertility treatments.
• Assisted Reproductive Technology (ART) data provides insights into clinical outcomes.

Purpose of the Study:

• To evaluate the efficiency and efficacy of oocyte cryopreservation using slow freezing versus vitrification.
• To compare oocyte cryopreservation outcomes with embryo cryopreservation and fresh IVF cycles.
• To analyze recent data from the Italian National Assisted Reproductive Technology Register (2009-2014).

Main Methods:

• Retrospective analysis of oocyte cryopreservation data from 2009-2014.
• Comparison of survival, implantation, and pregnancy rates between slow freezing and vitrification.
• Benchmarking oocyte cryopreservation against fresh oocyte IVF and embryo cryopreservation.

Main Results:

• Vitrification demonstrated significantly higher oocyte survival, implantation, and pregnancy rates than slow freezing (2009-2014).
• Substantial variation in success rates exists among centers, correlated with procedure volume.
• Fresh or cryopreserved embryo transfers yielded statistically better outcomes than those using embryos from cryopreserved oocytes.

Conclusions:

• Vitrification is the preferred method for oocyte cryopreservation due to superior results over slow freezing.
• Standardization of vitrification techniques is still needed for consistent outcomes.
• While vitrification is advancing, fresh embryo transfers and transfers from cryopreserved embryos show better performance, though results from experienced centers using cryopreserved oocytes are becoming comparable.