Time-lapse KIDScoreD5 for prediction of embryo pregnancy potential in fresh and vitrified-warmed single-embryo transfers

Research question: Can KIDScoreD5 predict which blastocysts have the highest potential for achieving pregnancy? Design: A retrospective cohort study of 670 single fresh or frozen (FET) embryo transfer cycles was conducted between May 2019 and June 2021 at the Ottawa Fertility Centre, Canada. Blastocysts obtained from stimulated eligible cycles and cultured in a time-lapse incubator were selected for transfer or cryopreservation based on Gardner morphological scoring. Implantation and viable pregnancy rates were analysed retrospectively using KIDScoreD5 and Gardner scores associated with the transferred embryos. The predictive power of the KIDScoreD5 and Gardner assessment was evaluated using the average area under the curve (AUC) of the receiver operating characteristic curve. Results: KIDScoreD5 was positively correlated with implantation (r = 0.96, P = 0.002) and viable pregnancy (r = 0.96, P = 0.0001) rates. In fresh embryo transfer cycles, the AUC for implantation rate was significantly higher for KIDScoreD5 compared with Gardner scoring (0.70 versus 0.63, P = 0.03). For FET, significantly higher AUC were calculated for KIDScoreD5 than for Gardner scoring, for both implantation (0.64 versus 0.54, P = 0.002) and viable pregnancy (0.63 versus 0.53, P = 0.002) rates. When the ranking of cryopreserved embryos was based on KIDScoreD5, 46.2% of the FET cycles had at least one unused sibling embryo with a better KIDScoreD5 than the one selected for FET based on Gardner assessment. Conclusions: KIDScoreD5 predicts implantation and viable pregnancy rates of blastocysts better than Gardner morphological assessment in single fresh or cryopreserved embryo transfer cycles.