To evaluate the outcome of oocyte vitrification using the Cryotop method, observed
in an egg donation program by simultaneously evaluating embryos derived from vitrified
and fresh oocytes coming from the same stimulated cycle.
Cohort prospective randomized study.
Instituto Valenciano de Infertilidad (IVI) Valencia, Spain.
Thirty oocyte donors and 30 recipients with informed consents.
Vitrification by the Cryotop method. Warming 1 hour after vitrification. Microinjection
of surviving MII and fresh oocytes, evaluation of fertilization, embryo development,
and clinical results.
Survival, fertilization, and cleavage rate. Embryo quality, pregnancy rate (PR), and
implantation rate.
Survival rate observed was 96.7%. There was no difference in fertilization rates (76.3%
and 82.2%), day 2 cleavage (94.2% and 97.8%), day 3 cleavage (80.8% and 80.5%), and
blastocyst formation (48.7% and 47.5%) for vitrified and fresh oocytes, respectively.
Embryo quality on day 3 and on day 5-6 were similar for vitrification and fresh oocyte
group (80.8% vs. 80.5% and 81.1% vs. 70%, respectively). A total of 23 embryo transfers
were carried out in the vitrification group. Pregnancy rates, implantation rates,
miscarriage rates, and ongoing PR were 65.2%, 40.8%, 20%, and 47.8%, respectively.
The Cryotop method preserves the potential of vitrified oocytes to fertilize and further
develop, which is similar, when evaluated simultaneously, to fresh counterparts. Excellent
clinical outcome indicates the possible use of this technology for egg donation programs,
as well as a high potential for establishing oocyte banking.