Impact of early cleaved zygote morphology on embryo development and in vitro fertilization–embryo transfer outcome: a prospective study

ObjectiveTo evaluate the impact of the first division morphology on embryo development and IVF–embryo transfer outcome.DesignProspective study.SettingTeaching hospital, France.Patient(s)All zygotes from 201 couples were checked for early cleavage. We defined as “even,” early cleaved (EC) zygotes with 2 cells of even size; as “uneven,” EC zygotes with 2 cells of uneven size; and as “fragmented,” EC zygotes with more than 20% fragmentation rate. Day 2 embryo quality was assessed as “top” embryo or “non-top,” with the evaluation of multinucleated blastomeres.Intervention(s)None.Main Outcome Measure(s)Day 2 embryo quality, pregnancy and implantation rates.Result(s)Among EC zygotes, 59.1% were even, 13.0% were uneven, and 27.9% were fragmented. Even EC yielded more “top” embryos and less multinucleated blastomere embryos than uneven EC (77.0% vs. 46.3%) and fragmented EC (77.0% vs. 13.9%). The 125 double embryo transfers that comprised at least one embryo derived from even EC zygote led to higher pregnancy rate (PR) (64.0% vs. 43.4%) and implantation rate (42.0% vs. 27.6%) compared to the 76 double embryo transfers with embryos derived from breakdown or 2PN zygotes.Conclusion(s)The morphology of the early cleaved zygote is involved in embryo development. Evaluation of this morphology is an effective and valuable method of assessing the embryo quality.