P–198 Higher rate of direct uneven cleavage (DUC) embryos in women exhibiting high ovarian response

Study question Does high ovarian response to controlled ovarian stimulation (COS) have a negative effect on oocyte quality? Summary answer High ovarian response is associated with reduced oocyte quality manifested as higher fraction of immature oocytes and higher rate of direct uneven cleavage (DUC) embryos. What is known already The literature regarding the effect of ovarian hyperstimulation on oocyte quality is limited and controversial. Results from several studies suggest that hyper response to controlled ovarian stimulation has a detrimental effect on oocyte and embryo quality, while others failed to confirm the existence of a direct toxic effect on oocyte and embryo quality. The association between temporal embryonal milestones and implantation rate has been previously demonstrated ,offering an additive tool by which oocyte quality, represented by embryo dynamics, can be evaluated. None of the aforementioned studies, however, used time lapse monitoring (TLM) system to evaluate oocyte and embryo quality. Study design, size, duration This study included a retrospective assessment of morphokinetic parameters performed by TLM from three university affiliated medical centers between January 2014 and December 2019. The developmental process and kinetics of 1863 embryos obtained from the study group, referred as the “ high ovarian response” (HOR) group, was compared to 4907 embryos from the control group - the “normal ovarian response” (NOR) group. Participants/materials, setting, methods The study included patients younger than 38 years who underwent COS with consecutive aspiration of either more than 15 oocytes (the HOR group) or 6–15 oocytes (the NOR group). A comparison was made between the groups regarding morphokinetic parameters, including the rate of embryos manifesting direct uneven cleavage (DUC) at first cleavage (DUC–1), as well as implantation and pregnancy rates. Logistic regression was conducted to assess the association between patients’ characteristics and implantation rate. Main results and the role of chance Oocyte maturation rate was significantly lower, and the DUC–1 embryos rate was significantly higher in the high ovarian response group compared to the normal ovarian response group (56.5% Vs 90.0%, p < 0.001 and 16.2% Vs 12.0%, p = <0.001; respectively). Following the exclusion of DUC–1 embryos, embryos from the HOR and the NOR groups reached the consecutive morphokinetic milestones at a similar rate and demonstrated similar implantation and clinical pregnancy rates. In a multivariate analysis preformed, only maternal age was found to be predictive for implantation. Limitations, reasons for caution The groups were not homogenous in their basic characteristics. Important information regarding the maximal dose of GT obtained, previous IVF response and ovarian reserve testing was lacking Wider implications of the findings: Higher oocyte quantity might have an effect on oocyte quality manifested as higher fraction of incompetent oocytes and higher rate of DUC–1 embryos. Once beyond the preliminary developmental stages, embryos from both groups reach the morphokinetic milestones at a similar rate and display similar implantation and pregnancy rates. Trial registration number Not applicable