Objective To determine whether single-day embryo selection (Day 3 or Day 5) achieves comparable sensitivity, specificity, and accuracy to two-day selection (Day 2 + Day 3 or Day 3 + Day 5). Design Retrospective cohort study conducted over a 15-year period (2008–2023). Setting A single assisted reproductive technology (ART) center. Participants A total of 9,095 patients undergoing ART were included: 7,365 were managed under a Day 3 policy (77,543 embryo assessments) and 1,730 patients under a Day 5 policy (14,538 embryo assessments). Methods All patients underwent routine ART procedures with morphological embryo scoring according to established criteria. Cleavage-stage selection based on a two-day assessment (Day 2 + Day 3) was compared with a hypothetical selection of a single-day assessment (Day 3). Blastocyst-stage selection based on a two-day assessment (Day 3 + Day 5) was compared with a hypothetical selection of a single-day assessment (Day 5). Sensitivity, specificity, and overall accuracy were calculated retrospectively for single-day versus two-day evaluation. Results Day 3 single-day assessment demonstrated sensitivity of 98.9%, specificity of 93.6%, and accuracy of 96.7%, comparable to Day 2 + Day 3 scoring. Day 5 single-day assessment yielded sensitivity of 99.5%, specificity of 89.7%, and accuracy of 93.4%, similar to Day 3 + Day 5 evaluation. Limitations Limitations of this study include the retrospective design and the inherently subjective nature of embryo selection, in which prior assessments can bias subsequent evaluations. In addition, two-day scoring reflected routine clinical practice, whereas single-day scoring represented a hypothetical approach based solely on embryo scores. This hypothetical single-day selection did not take the clinical context into account, as it was performed by a single embryologist based only on morphological scores, whereas actual clinical selection typically incorporates broader clinical considerations. Prospective randomized trials are therefor needed. Conclusion Single-day embryo selection on Day 3 or Day 5 provides diagnostic accuracy (≥90%) comparable to two-day protocols. Our data show that single-day assessments can be considered to cope with increased workload.
Mengels et al. (Wed,) studied this question.