P-229 Effect of morula pattern on clinical outcomes in single vitrified-warmed blastocyst transfer cycles
Authors: Kwon H  J , Cha J  H , Kim Y  J , Lee S  K , Kim J  H , Kim D  H , Lee J  H , Hur G  H , Woo S  M , Yoon J  W , Lee D  K , Kim H  Y , Pak K  A , Yoon J  S , Park S  Y 
Published: July 2024

Abstract

Study question
Does morula pattern affect clinical outcomes in single vitrified-warmed blastocyst transfer cycles?

Summary answer
Ongoing pregnancy rate is statistically increased when transferring the blastocyst derived from fully compacted morula in single vitrified-warmed blastocyst transfer cycles.

What is known already
Time-lapse microscopy has enabled the detailed identification and measurement of dynamic events of embryo development. Recent studies have shown that the exclusion of one or more cells from the compacted morula is associated with reduced developmental competence and a decrease in pregnancy rate. Additionally, it is also associated with decreased rates of PGT-A euploid and implantation. These findings demonstrate the correlation between morula pattern and the outcomes of assisted reproductive technologies.

Study design, size, duration
A retrospective cohort study was performed between January 2020 and November 2023. A total of 99 single vitrified-warmed blastocyst transfer cycles (women ≥ 35 years) were analyzed. The rates of biochemical pregnancy, clinical pregnancy, implantation, miscarriage, and ongoing pregnancy were evaluated.

Participants/materials, setting, methods
Images of morula stage embryos were collected at 7-focal planes and every 5-minute interval using a time-lapse microscope. The morula stage embryos were divided into two groups according to their compaction patterns. Morula stage embryos without excluded or extruded cells were defined as fully compacted morula (FCM, n = 47). In contrast, Morula stage embryos with excluded or extruded cells were defined as partially compacted morula (PCM, n = 52).

Main results and the role of chance
There were no differences of patient characteristics between FCM and PCM regarding female age (37.8 ± 2.1 vs. 37.8 ± 1.8, p = 0.96), number of previous IVF failure (0.5 ± 1.1 vs. 0.9 ± 1.6, p = 0.23), number of retrieved oocytes (16.1 ± 4.0 vs. 14.3 ± 5.1, p = 0.14), maturation rate (86.5% vs. 89.1%, p = 0.18), fertilization rate (73.8% vs. 69.9%, p = 0.39), survival rate (100% vs. 100%, p = Not applicable), and number of transferred embryos (1.0 ± 0.0 vs. 1.0 ± 0.0, p = Not applicable), with the exception of rate of good-quality embryos on Day 3 (44.7% vs. 37.6%, p = 0.04). No statistical differences were observed in rates of biochemical pregnancy (44.7% vs. 34.6%, p = 0.31), clinical pregnancy (40.4% vs. 26.9%, p = 0.15), miscarriage (11.4% vs. 15.4, p = 0.57), and implantation (40.4% vs. 26.9%, p = 0.15) between FCM and PCM, respectively. However, FCM demonstrated a significantly increased ongoing pregnancy rate compared to PCM (29.8% vs. 11.5%, p = 0.02).

Limitations, reasons for caution
This study was conducted with a small sample size, which limited the generalizability of the findings. Therefore, further studies are needed with a larger sample size and more diverse populations to confirm our findings.

Wider implications of the findings
The compaction pattern of morula stage embryos can be an indicator for embryo selection. The blastocyst derived from fully compacted morula has the potential to improve ongoing pregnancy rate in single vitrified-warmed blastocyst transfer cycles.

Trial registration number
not applicable