Embryo early cleavage, number of blastomeres and morphology at day three as factors to predict blastocyst development

Objective: the objective of this study is to evaluate markers of embryo quality, applied on day three of in vitro culture, in their capacity to predict whether embryos will reach blastocyst stage. Methods: a retrospective analysis of embryology database coming from 2772 zygotes obtained in 564 oocyte retrievals was performed; embryos were observed from day one to five: 23 to 26 hours after insemination all zygotes were evaluated to assess early cleavage, the number of blastomeres and embryo morphology were registered on day three and blastocyst formation was evaluated on day five; early first cleavage, number of blastomeres and embryo morphology at day three were correlated with embryo development until day five. Results: blastocyst formation rate was 36% in embryos with early cleavage and 19% in embryos without early cleavage, 43.6% in embryos with blastomeres and 12.8% in embryos with blastomeres at day three, the probability of a good quality embryo (grade 1 and 2a) at day three to reach the blastocyst stage was 48%, which was significantly higher than the chances of lower quality embryos. Conclusion: factors reported in this study - early cleavage, number of blastomeres and embryo morphology - are useful to decide a prolonged in vitro culture until day five. Key words: blastocyst, expanded blastocyst, early cleavage, blastomere number, embryo morphology.