P–778 Repeated cryopreservation process impairs embryo implantation potential but does not affect neonatal outcomes

Abstract

Abstract Study question Does repeated cryopreservation process effect embryo implantation potential and neonatal outcomes of human embryos? Summary answer Repeated cryopreservation impaired embryo implantation potential, resulting in a lower live birth rate and higher miscarriage rate, despite a comparable neonatal complication rate. What is known already With significant advances in the field of ART, the number of available embryos for transfer per cycle has also increased, resulting in a slew of surplus embryo cryopreservation. However, limited researches have focused on the embryonic development potential, clinical outcomes, pregnancy complications as well as the neonatal complications of embryos experiencing repeated cryopreservation. Study design, size, duration This was a retrospective, single-center cohort study. All ART cycles from January 2014 to December 2018. Age, body mass index, and number of oocytes retrieved were preferentially matched within a required range, with a total of 709 couples included in the study. Participants/materials, setting, methods The study was conducted in the Reproductive Medicine Centre affiliated to a university. Preferentially matched participants were divided into three groups according to the times of embryo cryopreservation: the fresh group (n = 249), the cryopreservation group (n = 244) and the re-cryopreservation group (n = 216). Embryo implantation rate, live birth rate, miscarriage rate, and neonatal complication rate were compared among these three groups. Main results and the role of chance The embryo implantation rate, clinical pregnancy rate and live birth rate in the re-cryopreservation group were significantly lower, and there was also a slight increase in the miscarriage rate. Logistic regression analysis indicated that embryos with repeated cryopreservation and lower TE scores were at higher risk of embryo implantation failure in single embryo transfer cycles (OR = 1.79 and 1.56 respectively). No significant differences were observed in gender, gestational age, birthweight, neonatal abnormality, and neonatal complications among the groups. Limitations, reasons for caution This was a retrospective cohort study conducted in single center. A multi-center prospective study with a larger sample size in well-matched participants is needed to reinforce our findings. Wider implications of the findings: Our findings demonstrated the adverse effect of repeated cryopreservation on embryo implantation potential. To avoid embryo waste, or in some special circumstances such as re-biopsy in PGT cycles, an additional cryopreservation on embryos was considered to be available to achieve clinical pregnancy and live birth. Trial registration number Not applicable