Transfer strategy performance varies with embryo morphokinetic quality in good prognosis IVF/ICSI cycles

Whether embryo morphokinetic quality influences the clinical efficacy of different embryo transfer (ET) strategies in good prognosis ICSI/IVF cycles remains an open question. This study evaluated the impact of early morphokinetic selection on clinical outcomes following fresh cleavage-stage single embryo transfers (FC-SETs) versus cryopreserved blastocyst single embryo transfers (CB-SETs). We conducted a retrospective cohort study analyzing 925 single embryo transfers, which included 565 FC-SETs and 360 CB-SETs. Embryos were ranked using an in-house Kinetic Evolution algorithm (KINEVO), whose performance was assessed through the relationship between KINEVO scores and live birth rates (LBR) following FC-SETs. Subsequently, clinical outcomes were compared across three distinct embryo cohorts: overall (n=925), top-quality (n=610) and non-top-quality (n=315). Pregnancy and live birth rates following FC-SETs were 57% and 51% higher (p ≤ 0.001) in A-score embryos as compared to non-A embryos. Multivariate analysis confirmed that the KINEVO score (OR = 1.62; p=0.015) and maternal age (OR = 0.88; p<0.0001) were independently associated with live birth. Overall, CB-SETs provided a higher clinical pregnancy rate (47.5% vs. 35.6%; p<0.0001) but a significantly higher miscarriage rate (21.6% vs. 9.5%; p=0.001) compared to FC-SETs. When a top-quality embryo was transferred, CB-SETs provided a numerically higher CPR (47.5% vs. 41.4%; p = 0.082) but a significantly higher miscarriage rate (21.4% vs. 10.5%; p = 0.011) as compared to FC-SETs, resulting in comparable live birth rates (37.4% vs. 36.5%; p = 0.46). Conversely, non-top-quality embryos achieved a 52% higher live birth rate (36.8% vs. 24.1%; p = 0.017) through CB-SETs as compared to FC-SETs. In conclusion, embryo quality must be controlled when alternative ET strategies are compared. FC-SETs can benefit patients and laboratory logistics when a top-quality embryo is produced, whereas a freeze-all strategy with CB-SETs may favor patients producing only sub-optimal embryos.