Abstract
Objective:In this study we investigate the correlation between spontaneous blastocyst collapse and pregnancy outcome.Methods:This is a retrospective study performed at Edinburgh Assisted Conception Programme, EFREC, Royal Infirmary of Edinburgh, UK. Embryos were cultured individually in 6.0% CO2, 5.0% O2, 89.0% N2, using single step medium (GTL™ Vitrolife, Göteborg, Sweden) and selected for transfer using standard morphological criteria. Using the EmbryoScope™ time-lapse monitoring (TLM), blastocysts collapse was analyzed by measuring the maximum volume reduction and defined as having collapsed if there was >50% volume reduction. Couples undergoing IVF/ICSI treatment and having an elective single embryo transfer (eSET) at blastocyst stage were included in this study. After the embryo transfer, retrospectively, each blastocyst was allocated to one of two groups (collapsed or not collapsed). 62 blastocysts collapsed once or more during development (17.4%), the remaining 294 showed no collapse (82.6%).Results:A significantly higher implantation rate (IR) of 61.2% and ongoing pregnancy rate (OPR) of 53.7% was observed when blastocysts which had not collapsed were replaced compared to cycles in which collapsed blastocysts were replaced (IR rate 22.6% and OPR 17.7%).Conclusion:This study demonstrated that human blastocysts which collapse spontaneously during in vitro development are less likely to implant and generate a pregnancy compared with embryos which do not. Although this is a retrospective study, the results establish the utility of collapse episodes as new marker of embryo selection following eSET at blastocyst stage.
Highlights
Over the past forty years assisted reproductive technologies (ART) have evolved considerably from and ambitious and experimental procedure to a mainstream medicine which has brought more than 7 million children to the world (De Geyter et al, 2018)
The system does not cover all aspects of blastocyst morphology it has been very effective in classifying the appearance and compactness of the inner cell mass (ICM), the cohesiveness and number of trophectoderm cells (TE) and degree of expansion of the blastocoel cavity
In this study we included only elective single embryo transfer (eSET) at blastocyst stage, and embryo implantation was confirmed by an ultrasound scan for gestational sac with fetal heartbeat after seven weeks of pregnancy
Summary
Over the past forty years assisted reproductive technologies (ART) have evolved considerably from and ambitious and experimental procedure to a mainstream medicine which has brought more than 7 million children to the world (De Geyter et al, 2018). Blastocoel formation starts through an initial secretion between the morula cells: the small cavity is maintained and increased by actions of the membrane channels such as the Na+/K+-ATPase enzyme, which raises the salt concentration within the embryo, attracting water through osmosis (Watson et al, 2004). The increased water pressure gradually increments the size of the cavity which continues throughout the blastocyst formation (Baltz et al, 1997). TE cells secrete lysine that is involved in zona pellucida (ZP) thinning and hatching. Blastocyst expansion, as well as ZP thinning and hatching in vitro have been described by TLM in several mammals (Gonzales et al, 1996; Glass et al, 1973; Gonzales & Bavister, 1995; Seshagiri et al, 2009)
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