Embryo cryopreservation: proposal for a new indicator of efficiency

Area of Science:

• Reproductive Medicine
• Embryology
• Cryobiology

Background:

• Embryo cryopreservation is a key component of assisted reproductive technologies.
• Standard reporting of pregnancy rates (PR) in literature often uses PR per embryo transfer (ET).
• This method may not fully account for embryo losses during the cryopreservation and thawing process.

Purpose of the Study:

• To compare the relevance of PR per thawed embryo versus PR per ET for expressing embryo cryopreservation results.
• To determine if accounting for embryo losses provides a more accurate assessment of outcomes.

Main Methods:

• Systematic review of 102 articles published between January 1983 and February 2009.
• Analysis focused on human cryopreserved embryo thawing.
• Compared PR per ET with PR per thawed embryo, considering embryo loss.

Main Results:

• Statistical analysis revealed significant differences in outcomes when accounting for embryo losses.
• The rate of thawed transferred embryos, which accounts for embryo losses, proved to be a good prognostic factor for PR.
• Some statistical comparisons yielded different results depending on the reporting method used.

Conclusions:

• Reporting pregnancy rates per thawed embryo, which incorporates embryo loss, can yield different conclusions than traditional methods.
• This metric offers a more informative approach for accurate analysis of clinical practices in embryo cryopreservation.