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Vitrification of human blastocysts using cryoloops: clinical outcome of 223 cycles
T Mukaida1, S Nakamura, T Tomiyama
1Hiroshima HART Clinic, 5-7-10 Ohtemchi, Naka-ku, Hiroshima, Osaka HART Clinic, Snowcrystal 10F 2-6-20, Umeda, Kita-ku, Osaka, Japan.
Background:
The need to cryopreserve human blastocysts is increasing. The successful birth has been reported of a baby from a blastocyst vitrified using the cryoloop technique. The present study expands on this earlier report to confirm the effectiveness of this vitrification procedure.
Methods:
In patients undergoing IVF at one of three clinics, supernumerary blastocysts on day 5 or 6 at various stages of development were vitrified using cryoloops.
Results:
Of 725 vitrified blastocysts, 583 (80.4%) survived. After the transfer of 493 blastocysts in 207 cycles, 76 women (37%) became clinically pregnant. Among these women, 21 pregnancies ended in miscarriage, 23 healthy babies were born in 18 deliveries, and 37 pregnancies are ongoing. The survival rate of day 5 blastocysts (87%) was higher than that of day 6 blastocysts (55%), but implantation rates and pregnancy rates were not statistically significantly different.
Conclusions:
Clinical outcomes with 725 blastocysts and 207 transfers showed that vitrification using cryoloops is effective and practical for the cryopreservation of human blastocysts. Early blastocysts on day 5 seem to be the most suitable in terms of stage and age for cryopreservation, but developed and day 6 blastocysts can also be cryopreserved.