PurposeThe time‐lapse system is a device that allows continuous monitoring without removing embryos from the incubator. Using a time‐lapse system, we retrospectively investigated cleavage speed time points as potential indicators for selecting high‐quality viable blastocysts.MethodsThis study included 963 zygotes of two pronuclei retrieved from 196 patients between January 2015 and December 2016. All embryos in culture were monitored by time‐lapse after intracytoplasmic sperm injection. Of 492 blastocysts developed in vitro, 128 vitrified‐warmed single blastocyst transfers were classified into pregnancy and non‐pregnancy groups, and the parameters were compared.ResultsIn the pregnancy group, timing of both morula compaction and regular blastocyst formation was significantly faster than in the non‐pregnancy group. Furthermore, the optimal cutoff values for compacted morula (94.9 hours) and regular blastocyst (113.9 hours) were determined using the receiver operator characteristic curve analysis. Embryos that formed compacted morulae within 94.9 hours and developed into regular blastocysts within 113.9 hours were associated with a significantly higher pregnancy rate than those that did not (44.4% vs 16.0%).ConclusionThe timing of morula compaction and regular blastocyst formation is important as an indicator of high‐quality blastocysts to increase odds for pregnancy after embryo transfer.
The objectives of this study were to evaluate the impact of two different sizes of zona pellucida thinning area by laser assisted hatching on the clinical outcome of cryopreserved cleaved embryos (Experiment 1) and two different sizes of zona pellucida opening area by laser assisted hatching on the clinical outcome of cryopreserved cleaved embryos that were cultured to blastocyst (Experiment 2). A total of 120 cryopreserved cleaved embryo transfers were assigned to either quarter or half of zona pellucida thinning group. Laser assisted hatching was conducted at the cleavage-stage. The rates of clinical pregnancy (47 versus 25%) and implantation (32 versus 16%) were significantly greater in the half thinning group than in the quarter thinning group (P = 0.0218 and P = 0.0090, respectively) (Experiment 1). A total of 71 cryopreserved cleaved embryo transfers were assigned to either one eighth or half of zona pellucida opening group. The cryopreserved cleaved embryos were cultured to blastocyst and laser assisted hatching was conducted at the blastocyst-stage. The rates of clinical pregnancy (74 versus 43%) and implantation (52 versus 27%) were significantly greater in the half opening group than in the one eighth opening group (P = 0.0090 and P = 0.0117, respectively) (Experiment 2). Our results suggest that the size of zona pellucida thinning area or opening area can affect the clinical outcome of cryopreserved cleaved embryo transfers.
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