P-199 The development time of good quality blastocysts is dependent on their genetic status in patients over 36 years old
Authors: Zakharova E , Troshina T , Sheremet A , Kuzmina K , Novikova E 
Published: July 2024

Abstract

Study question
Is there any difference in PGT-A results between good quality blastocysts depending on whether they reach this stage on the fifth or sixth day?

Summary answer
In patients over 36 years old, there is a significantly higher rate of aneuploidy in embryos that reach the blastocyst stage on Day 6.

What is known already
The level of chromosomal abnormalities in embryos increases with maternal age, as indicated by PGT-A data. Embryo quality also correlates with aneuploidy level. The normal timeframe for blastocyst formation is considered to be between the fifth and sixth day of development. In this study, the genetic status of good quality blastocysts was examined to determine a difference in the aneuploidy rate between blastocysts formed on the fifth day compared to those formed on the sixth day.This information could provide insights into the optimal timing for blastocyst formation and its relationship to genetic abnormalities. Embryo quality also correlates with aneuploidy level

Study design, size, duration
The retrospective study included 513 good quality blastocysts (3-4, A-B according to the Gardner classification) after trophectoderm biopsy and obtained from fresh oocytes of 141 patients aged 23-45 years. The PGT-A data were analyzed. The analysis considered the age of the patients, with one group of patients younger than 36 years old (35 patients, 174 blastocysts), and another group aged 36 years and older (106 patients, 339 blastocysts).

Participants/materials, setting, methods
Trophectoderm biopsy was performed on good quality embryos as they progressed in development, either on the fifth or sixth day. PGT-A was conducted using the NGS method, and the data was processed using the chi-square test.

Main results and the role of chance
Among patients younger than 36 years old, 58.5% of good quality blastocysts formed by the fifth day of development. In comparison, among patients 36 years old and older, 43.0% of good quality blastocysts formed by the fifth day. The difference in the growth rate of blastocysts of the same quality between the age groups was statistically significant (p &gt; 0.01). In patients younger than 36 years old, 75.0% of blastocysts formed by the fifth day and 66.7% of blastocysts formed by the sixth day were euploid (with no significant difference). In patients 36 years old and older, 50.5% of blastocysts formed by the fifth day were euploid, while only 19% of blastocysts formed by the sixth day were euploid. This difference in euploidy rates between the fifth- and sixth-day blastocysts was statistically significant (p &gt; 0.01).

Limitations, reasons for caution
The study was conducted with a relatively small sample size, which may limit the generalizability of the results. A larger and more diverse sample would be beneficial to confirm the findings.

Wider implications of the findings
In patients over 36 years of age, the majority of blastocysts develop by Day 6, and there is a significant increase in aneuploidy level. This suggests that there may be a higher risk of chromosomal abnormalities in embryos that take longer to develop into blastocysts in this group.

Trial registration number
Not applicable