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BACKGROUND: Since we reported the first successful birth from a blastocyst vitrified using a cryoloop technique, our results showed that the survival rate of vitrified blastocysts was negatively correlated with the expansion of the blastocoele. We speculated that a large blastocoele may disturb the efficacy of vitrification. Therefore, we evaluated the effectiveness of artificial shrinkage (AS) of blastocoeles before vitrification, on increasing the survival rate of vitrified blastocysts. METHODS: Supernumerary expanded blastocysts on day 5 were vitrified after AS, which was performed by puncturing the blastocoele with a micro-needle, or by making a hole in the blastocoele with a laser pulse. After warming, viable blastocysts (confirmed by re-expansion of the blastocoele) were transferred to patients with hormone replacement cycle. We compared these data with those of our previous report where AS was not carried out. RESULTS: The survival rate was significantly higher (97.2%, 488/502) in this study than that of the previous report (86%). After 266 transferable cycles, 160 patients became pregnant (60.2%), which was significantly higher than our previous results (34.1%, 29/85). The implantation rate was 46.7% (209/448). CONCLUSIONS: Our results revealed that the survival rate and the pregnancy rate of vitrified expanded and hatching blastocysts can be improved by using AS to collapse the blastocele before vitrification.

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.

OBJECTIVE: Vitrification has been recognized as a useful method for cryopreservation of human blastocysts (BLs). However, a major drawback is the use of a relatively high concentration of cryoprotectants, and the higher incidence of MZT(monozygotic twinning). Therefore, we analyzed perinatal incidence after 13 weeks of gestation including the rate of MZT in infants born after vitrified BL. DESIGN: Retrospective analysis. MATERIALS ANDMETHODS: Perinatal outcome were summarized for all patients who had vitrified BL transfer cycles between 2000 and 2010. Vitrification involved the exposure DMSO and EG during the cooling step, and 0.25/0.5 M sucrose solution for warming. The blastocoelic cavity was collapsed with laser pulse, prior to vitrification. After warming, zona hatching was carried out. MZT was defined that the number of FHB was more than that of embryos transferred. RESULTS: A total of 8960 vitrified BLs from 5434 cycles were warmed and 8432 survived (94.1%). In 5347 transfers, 2568 resulted in pregnancy (48.0%). A total of 7532 vitrified BLs were transferred and 2882 were implanted (38.3%). A total of 1751 children(899boys & 852girls) were born in 1533 deliveries. Forty one clinical pregnancies were confirmed as MZT(2.7%). Thirty three cases had either congenital birth defects or perinatal complications (1.9%), including six chromosomal abnormalities (two 18, four 21 trisomy), six multiple anomalies, one stillbirth due to hydropus, four stillbirths of unknown causes, one anencephaly, one spina bifida, nine congential heart malformations, one esophageal and one biliary duct obstruction, one Cornelia De Lange, and one Treacher Collins syndrome. CONCLUSION: The perinatal results of 1517 deliveries of 1735 babies, the incidence rate of MZT (2.7%) and rate of congenital defect and neonatal complication (1.9%) that were both similar to fresh BL transfer as we reported previously (2.3% & 2.0%), confirm the safety of vitrified BL program. Also, the high implantation rate encourages us to establish single BL transfer.