P-208 To assess or not to assess: reconsidering day 3 embryo quality in planned freeze-all blastocyst cycles
Authors: Barbagallo B  M , Marzanati D , Bartolacci A , Solano Narduche L , D’Alessandro G , Rabellotti E , Papaleo E , Pagliardini L 
Published: July 2024

Abstract

Study question
Should day 3 embryo quality assessment be consider in planned freeze-all blastocyst cycles?

Summary answer
Day 3 embryo assessment may be unnecessary in planned freeze-all blastocyst cycles.

What is known already
Day 3 embryo quality is a predictor of in vitro fertilizastion (IVF) success rates in cleavage stage embryo transfer. However, the association between day 3 embryo quality and live birth in blastocyst transfer policy is largely unknown.

Study design, size, duration
This retrospective study included 1074 frozen-thawed single day 5/6 blastocyst transfer between January 2019 to December 2022. Three groups were assessed depending on whether the transferred blastocyst derived from a top-quality, good-quality or poor-quality embryo at day 3. The analysis was conducted independently for each blastocyst quality group (top, good, and poor) using multivariate logistic regression. We applied factor analysis of mixed data to reduce potential collinearity between covariates used in the model.

Participants/materials, setting, methods
All blastocysts included in this study were obtained from first ICSI freeze-all cycles. Cleavage stage and blastocyst evaluation were performed according to the Istanbul consensus. Cleavage and blastocysts stage were assessed between 67±0.5 (day-3), 115±0.5 (day-5) and 139±0.5 (day-6) hours post-insemination (hpi), respectively. Exclusion criteria were: i) ICSI-cycles performed with surgically retrieved or frozen sperm, (ii) gamete donation cycles, (iii) cryopreserved-thawed oocyte cycles, (iv) preimplantation genetic testing. The primary outcome was live birth rate.

Main results and the role of chance
After adjusting for the day of transfer (day 5 or day 6) and several confounding variables, no statistical differences in live birth were observed among same quality blastocysts derived from different day 3 embryo quality groups (top=A, good=B and poor=C). The analysis was stratified for different blastocyst quality groups:
1) top quality blastocyst [day 3 quality A =reference group; day 3 quality B= OR 1.04 95% CI (0.62 – 1.74), p value=0.871; day 3 quality C= OR 0.67 95% CI (0.34 – 1.33), p value= 0.254]
2) good quality blastocyst [A =reference group; B= OR 0.80 95% CI (0.49 – 1.30), p value=0.361; C= OR 0.74 95% CI (0.44 – 1.27), p value= 0.276]
3) poor quality blastocyst [A =reference group; B= OR 0.78 95% CI (0.29 – 2.10), p value=0.622; C= OR 0.80 95% CI (0.31 – 2.07), p value= 0.650].

Limitations, reasons for caution
The study is limited by its retrospective design. Embryo assessment without time-lapse technology, to assess the blastocysts at the same developmental time-frame, is another limitation; although the static observation time very close and restricted to the Istanbul consensus guidelines may mitigate such a weakness.

Wider implications of the findings
Our findings showed that day 3 embryo quality assessment may be unnecessary in planned freeze-all blastocyst cycles. In the context of static embryo assessment, this can reduce the stress on embryos by avoiding unnecessary retrievals from incubators.

Trial registration number
not applicable