P-114 The timing from post-insemination to blastocyst vitrification correlates with ploidy and gender
Authors: Baatarsuren M , Baljinnyam L , Ganbaatar C , Sengebaljir D , Erdenekhuyag B , Enkhbaatar S , Tumur-Ochir G , Amarsaikhan A , Dorjpurev A , Ganbat G , Boris T , Khangarid A , Jamiyansuren J 
Published: July 2024

Abstract

Study question
Which morphology parameter of blastocysts has the strongest correlation with the euploid rate?

Summary answer
The vitrification times post-insemination and trophectoderm grade (TE) are more predictive parameters for euploid blastocysts, and female blastocysts require less time for vitrification.

What is known already
In current ART, the use of preimplantation genetic tests for aneuploidy (PGT-A) has increased by 2 to 25 percent in different countries. PGT-A analyses have helped patients achieve an increased pregnancy rate, choose the gender of the embryo and prevent miscarriages. Moreover, the potential for blastocyst euploid is strongly correlated with the developmental speed and morphology grades. However, for patients without PGT-A, the criteria for selecting transferred blastocysts are mostly based on morphology and the day of the blastocyst. Therefore, it is essential to clarify which parameter is more predictive of euploid embryos during elective FET cycles.

Study design, size, duration
This retrospective analysis included 713 blastocysts from 417 patients treated at the Ojinmed IVF Center, Mongolia, between May 2019 and June 2023. The morphology parameters (morphology grade, blastocyst formation time, vitrification time and inner diameter) were compared between the PGT-A results and the control results. Blastocyst quality was evaluated with the Gardner and Schoolcraft grading system, and the inner diameter of the blastocyst was measured.

Participants/materials, setting, methods
All patients underwent a clomiphene-based minimal ovarian stimulation protocol or drug-free natural cycle of IVF treatment. When the blastocyst diameter exceeded 160 μm, a trophectoderm (TE) biopsy was taken, and the blastocyst was immediately vitrified using the Cryotop method. The time of vitrification and formation of the blastocyst were recorded from the insemination. The patients were analyzed using high-resolution NGS PGT-A (10 Mb resolution for copy number variations and 30%-70% for mosaicism).

Main results and the role of chance
The PGT-A analysis reported euploid, aneuploid, and mosaic rates. Euploid, aneuploid, and mosaic rates were significantly correlated with blastocyst formation time (114.78 ± 4.49 h, 116.12 ± 6.42 h and 116.33 ± 6.87 h, p = 0.003) and vitrification blastocyst time (126.65 ± 9.8 h, 131.57 ± 10.8 h and 130.44 ± 11.19 h, p &lt; 0.001), along with women’s age (34.9 ± 4.32, 38.14 ± 3.77, and 35.84 ± 4.5, p &lt; 0.001). In logistic regression analysis, aneuploid rates were significantly lower in blastocysts with A and B grade of ICM (OR 0.36, CI 95% 0.24-0.32, p &lt; 0.01 and OR 0.45, CI 95% 0.32-0.63, p &lt; 0.01) and A and B grade of TE (OR 0.20, CI 95% 0.11-0.37, p &lt; 0.01 and OR 0.20, CI 95% 0.25-0.48, p &lt; 0.01) compared to C grades, respectively. The AUCs for prediction of euploid were maternal age 0.66 (95% CI 0.62-0.70), TE grade 0.64 (95% CI 0.57-0.64), blastocyst vitrification time 0.62 (95% CI 0.58-0.66), ICM grade 0.60 (95% CI 0.61-0.68), blastocyst formation time 0.55 (95% CI 0.51-0.59) and inner diameter 0.46 (95% CI 0.42-0.5). Although blastocyst vitrification time is correlated with blastocyst gender (female blastocyst 127.9 ± 10.25h vs male blastocyst 129.68 ± 10.84h, p = 0.02).

Limitations, reasons for caution
The results of the retrospective study are limited to data from a single IVF center and conventional incubators were used in this study.

Wider implications of the findings
These findings might help non PGT-A patients in deciding on embryo selection for transfer. The vitrification time and TE grade of blastocysts are strongly correlated with euploid rate than the ICM, inner diameter and formation time. Also, female blastocysts take less time to vitrification time than male blastocysts.

Trial registration number
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