P-121 Post-warming morphokinetics as a predictive tool for embryo implantation
Authors: Cavagnoli M , Braga D , Setti A , Guilherme P , Tomioka R , Iaconelli Junior A , Borges E 
Published: July 2024

Abstract

Study question
Does frozen-thawed blastocyst morphokinetics observed using time-lapse imaging provide an indicator for implantation in intracytoplasmic sperm injection (ICSI) cycles with deferred embryo transfers?

Summary answer
The blastocyst morphokinetic behavior after warming may provide an indicator for implantation in ICSI cycles.

What is known already
Embryo cryopreservation has become a pivotal component in assisted reproduction, applicable both to surplus embryos and in freeze-all cycles. Throughout vitrification and warming processes, embryos face considerable challenges. Historically, the evaluation of fresh blastocysts has relied on the examination of morphological features and the assessment of blastocoel expansion, trophectoderm, and inner cell mass. However, for vitrified and warmed blastocysts, traditional evaluation may not suffice to predict implantation. The emergence of a TLI culture system has facilitated a comprehensive examination of embryo development. Hence, post-warming culture in TLI incubators may provide a more precise assessment of vitrified and warmed blastocyst behavior.

Study design, size, duration
From January to October 2022, an observational cohort study was conducted at a private university-affiliated IVF centre. This included 411 vitrified/warmed blastocysts, from freeze-all cycles, with known implantation data (no implantation and full implantation per transfer), which were evaluated by TLI. Blastocyst morphological dynamics variables after warming were recorded, and their potential association with clinical pregnancy was investigated using Generalized linear models (GzLM) adjusted for oocyte age, followed by Bonferroni post hoc test.

Participants/materials, setting, methods
After warming, the recorded factors were: (i) initial blastocyst area (IBA); (ii) maximum blastocyst area (MBA); (iii) Blastocyst area delta (DBA); (iv) initial ZP thickness (IZP); (v) minimum ZP thickness (MZP); (v) ZP thickness delta (delta ZP area); and (iv) blastocyst expansion (BE). Embryos received a final score from 0 to 9, according to the sum of the scores from each parameter and were grouped as: Low total-score, medium total-score), and high total-score.

Main results and the role of chance
No significant difference was observed when maternal age (37.8 ± 5.3, 37.2 ± 5.2, and 37.4 ± 5.7, for low, medium and high total-score groups respectively, p = 0.743) and oocyte age (34.9 ± 4.9, 34.1 ± 4.7, and 33.7± 5.2, for low, medium and high total-score groups respectively, p = 0.229) were compared between the score groups. A significant increase in the implantation rate was noted among embryos presenting higher scores, followed by those with median scores, while embryos with lower scores presented the lowest implantation rate (34.8 ± 5.3, 35.9 ± 5.2, and 39.7 ± 5.2, for low, medium and high total-score groups respectively, p &lt; 0.001). No significant differences in the miscarriage rate were observed between the three score groups (10.0 ± 4.2, 13.2 ± 4.1, and 5.1 ± 2.9, for low, medium and high total-score groups respectively, p = 0.239.) The logistic regression analysis showed that embryos in the low total-score group presented a 12.3% decreased chance of implantation when compared with embryos in the high total-score group (OR: 0.877, CI: 0.843-0.912, p &lt; 0.001), while embryos in the medium total-score group presented a 9.6% decreased implantation chance when compared with embryos in the high total-score group (OR: 0.904, CI: 0.870-0.939, p &lt; 0.001).

Limitations, reasons for caution
The use of historical cohort groups is a drawback.

Wider implications of the findings
The behavior of blastocysts after warming, as indicated by blastocyst area, ZP thickness, re-expansion, along with the pre-vitrification embryo classification, may provide crucial information for selecting the optimal embryo for transfer and managing patient expectations.

Trial registration number
N/A