Relationship between a novel assessment scoring system in pre-implantation genetic testing for aneuploidy and clinical outcomes after embryo transfer: a single-center retrospective cohort study

Background The evaluation and interpretation of mosaicism in pre-implantation genetic testing for aneuploidy (PGT-A) can be complex, and no consensus or standardized criteria are available for its assessment. We investigated whether mosaicism as assessed by the proprietary Knowledge-based Aneuploidy Theoretical Score (KAT-Score) in PGT-A correlates with clinical pregnancy and live birth rates. Methods This retrospective cohort study was conducted in a single in vitro fertilization center between August 2020 and March 2023. A total of 124 single vitrified-warmed blastocyst transfer cycles were analyzed for clinical outcomes stratified by KAT-Score. We also analyzed the correlations between KAT-Score and clinical pregnancy or live birth rates. Results We found no significant difference in the KAT-Score between the pregnancy and non-pregnancy groups. However, the KAT-Score was significantly lower in the live birth group than in the non-live birth group. Moreover, the KAT-Score was a predictive indicator of live birth (area under the curve = 0.64, P  < 0.01) but not of clinical pregnancy (area under the curve = 0.56, P  = 0.1597). Multivariate logistic regression analysis, which included maternal age, previous embryo transfer cycles, endometrial thickness, and morphological grade as confounding factors, showed that lower KAT-Scores significantly correlated with the live birth rate (adjusted odds ratio: 0.83, 95% confidence interval: 0.70–0.99, P  = 0.0403). No eventual live births were recorded in the group with a KAT-Score indicative of high chromosomal mosaic gain (KAT-Score ≥ 7). Conclusions This study suggests that the KAT-Score correlates with live birth but not with clinical pregnancy. The live birth rate differed according to type of mosaicism.