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Validation of Optimized Embryo Scoring Procedures: Single-Day versus 2-Day Assessment
Annemie Mengels1, Annouschka Laenen2, Carl Spiessens3
1Department of Obstetrics and Gynaecology, Leuven University Fertility Centre, University Hospital Leuven, Leuven, Belgium, annemie.mengels@uzleuven.be.
Objective:
The aim of this study was to determine whether single-day embryo selection (day 3 or day 5) achieves comparable sensitivity, specificity, and accuracy to 2-day selection (day 2 + day 3 or day 3 + day 5).
Design:
This was a retrospective cohort study conducted over a 15-year period (2008-2023).
Setting:
The review was conducted in 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 2-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 2-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 2-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, 2-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 therefore needed.
Conclusion:
Single-day embryo selection on day 3 or day 5 provides diagnostic accuracy (≥90%) comparable to 2-day protocols. Our data show that single-day assessments can be considered to cope with increased workload.
