A monocentric analysis of the efficacy of extracellular cryoprotectants in unfrozen solutions for cleavage stage embryos

Francesco Capodanno, Jessica Daolio, Gaetano De Feo, Angela Falbo, Daria Morini, Alessia Nicoli, Luca Braglia, Maria Teresa Villani, Giovanni B. La Sala, Lodovico Parmegiani, Lorenzo Aguzzoli

Research output: Contribution to journalArticlepeer-review


Background: In the absence of international guidelines indicating the usage of vitrification rather than slow-freezing, the study aim was to analyze a large cohort of slow-frozen/thawed embryos to produce a rationale supporting the standardization of IVF cryopreservation policy. Methods: This retrospective analysis included 4779 cleavage stage embryos cryopreserved by slow-freezing/thawing from September 2009 to April 2017 at a single Center. Biological and clinical outcomes of three different commercial kits adopted sequentially, i.e. Vitrolife Cleave Kit® from Vitrolife (kit 1) vs. K-SICS-5000 Kit® and K-SITS-5000 Kit® from Cook Medical (kit 2) and Freeze/Thaw 1™ Kit® from Vitrolife (kit 3) were collected and compared in the light of cryoprotectants composition. Results: Kit 3 compared to kit 1 and kit 2 showed significantly (P < 0.001) higher embryo survival (79.9% vs. 75.6 and 68.1%, respectively) and frozen embryo replacement (91.5% vs. 86.5 and 83.3%, respectively) rates, and significantly (P < 0.001) lower blastomere degeneration rate (41.5% vs. 43.6 and 52.4%, respectively). No significant difference for clinical outcomes was observed among kits. Only a slight positive trend was observed for kit 3 vs. kit 1 and kit 2 on delivery rate per thawing cycle (7.12% vs. 4.19 and 4.51%, respectively; P < 0.058) and live birth rate (3.07% vs. 2.59 and 1.93%, respectively, P < 0.069). Thawing solutions of kit 3 were similar to those of any warming protocol. Conclusions: A defined concentration of extracellular cryoprotectants in thawing/warming solutions had a beneficial effect on the embryo cryosurvival rate. Results could provide the rationale for the adoption of a single standardized warming protocol.

Original languageEnglish
Article number84
JournalReproductive Biology and Endocrinology
Issue number1
Publication statusPublished - Oct 27 2019


  • ART
  • Cryopreservation
  • IVF
  • Slow-freezing
  • Vitrification
  • Warming

ASJC Scopus subject areas

  • Reproductive Medicine
  • Endocrinology
  • Obstetrics and Gynaecology
  • Developmental Biology


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