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Purpose The aim of this study was to determine if the size of zona pellucida thinning area by laser assisted hatching could affect the rates of pregnancy and implantation for vitrified-warmed embryo transfers at the cleavage-stage. Methods A total of 120 vitrified-warmed cleavage-stage embryo transfers were randomly assigned to either quarter or half of zona pellucida thinning group. Results The rates of clinical pregnancy (46.7 versus 25.0%) and implantation (32.0 versus 16.2%) were significantly greater in the half thinning group than in the quarter thinning group ( P  = 0.0218 and P  = 0.0090, respectively). Conclusions The results of this investigation show that, in vitrified-warmed embryo transfers at the cleavage-stage, the size of zona pellucida thinning area by laser assisted hatching impacts the rate of clinical pregnancy and implantation and that half of zona pellucida thinning significantly increases both of these results compared with quarter of zona pellucida thinning.

Purpose To evaluate the effect of the size of zona pellucida opening by laser assisted hatching for frozen cleaved embryo that were thawed after both fresh and frozen cleaved embryo transfer cycles failed and were cultured to blastocyst after thawing in patients with multiple implantation failures. Materials and methods Of 101 consecutive procedures (October 2003 to June 2006), 30 patients declined to perform assisted hatching and were selected as control group, 40 patients had 40 μm opening of the zona (October 2003 to January 2005), 31 patients had 50% of the zona opening (February 2005 to June 2006). Results The pregnancy, implantation and delivery rates were significantly higher in 50% opening group (74%, 52% and 65%) compared to control group (17%, 10% and 13%; P  < 0.01) and 40 μm opening group (43%, 27% and 38%; P  < 0.04). Conclusions The size of the zona pellucida opening may affect the outcome of frozen cleaved embryo transfer.

Purpose To report a successful delivery after the transfer of a re-cryopreserved day-7 hatched blastocyst. Methods and Results A 30-year-old woman underwent a long-treatment protocol for ovarian stimulation. Fourteen mature oocytes were obtained, and twelve were fertilized. On day 3, two cleaved embryos were transferred, but no implantation occurred. The remaining embryos were vitrified. Subsequently, two vitrified day-3 embryos were transferred. The woman became pregnant and delivered a healthy baby. Subsequently, two vitrified day-3 embryos were transferred, but no pregnancy occurred. Subsequently, all the remaining vitrified day-3 embryos were cultured. On day 5, no blastocyst was obtained. The remaining embryos were continued to be cultured. On day 7, a hatched blastocyst was obtained and re-vitrified. Subsequently, the re-vitrified day-7 hatched blastocyst was transferred. The woman became pregnant and delivered a healthy female. Conclusions The day-7 hatched blastocyst developed from vitrified embryos can be re-vitrified and have pregnancy potential after re-warming.

To report successful pregnancies after the transfer of re-vitrified human day 7 blastocysts developed from vitrified cleaved embryos. A total of five day 7 blastocysts developed from vitrified cleaved embryos were re-vitrified and re-warmed. All of five re-vitrified day 7 blastocysts (100%) survived after warming and were transferred to three patients. Two of the women became clinically pregnant. Of these women, one woman delivered a healthy baby and the other pregnancy is ongoing at 26 weeks of gestation. This is the first report of successful pregnancies after the transfer of re-vitrified human day 7 blastocysts developed from vitrified cleaved embryos.