A prospective comparison of outcome following cryopreservation using vitrification vs. a modified slow-freeze protocol of 2 pronuclear (2PN) and day 3 multi-cell embryos.
OBJECTIVE
To compare the efficacy of vitrification of 2 pronuclear and day 3 cleavage stage embryo vs. a modified slow freeze protocol that historically has achieved good survival and pregnancy rates at these stages.


METHODS
Embryos were randomly assigned by day to freezing at the 2 proncular stage or day 3 cleavage stage embryos by either vitrification or a modified slow freeze protocol. Comparisons were made for survival rate, cleaveage rate, and pregnancy rate.


RESULTS
The results were comparable with a slight edge to vitrification. Only the implantation rates of day 3 cleavage staged embryos (75% vs. 30.4%) showed a significant difference.


CONCLUSIONS
Vitrification seems to be equally or possibly slightly superior to freezing embryos at the 2 pronuclear or day 3 cleavage stage vs. a modified slow freeze protocol that had been previously found to be superior to the slow freeze method of LaSalle-Testart.
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D000328:Adult; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation / Q000379:methods*; D010064:Embryo Implantation; D004624:Embryo Transfer / Q000379:methods; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods; D006801:Humans; D011247:Pregnancy; D018873:Pregnancy Rate; D011446:Prospective Studies; D058989:Vitrification