Evaluating the impact of morphological parameters and developmental speed on blastocyst ploidy and sex: A...

In assisted reproductive technology (ART), transferring a single euploid blastocyst optimizes pregnancy outcomes and reduces the risk of multiple gestation. Chromosomal aneuploidy, relatively prevalent among patients of advanced maternal age, remains a leading cause of ART failure. This study investigated the relationships among blastocyst morphology, developmental speed, ploidy status, and sex.

This retrospective cohort study analyzed 856 blastocysts from 439 patients who underwent minimal stimulation in vitro fertilization (IVF) cycles at the Ojinmed IVF Center, Mongolia, between May 2019 and June 2024. Embryo grading followed the Gardner and Schoolcraft system, assessing blastocyst expansion, inner cell mass grade, trophectoderm (TE) grade, and developmental timing. TE biopsies were evaluated for euploidy, whole or segmental aneuploidy, and mosaicism.

Euploidy, aneuploidy, and mosaicism rates were 49.8%, 33.4%, and 16.8%, respectively, exhibiting significant correlations with maternal age. Women at least 35 years old faced increased aneuploidy risk (adjusted odds ratio [aOR], 3.34; 95% confidence interval [CI], 2.35 to 4.61; p<0.001) and reduced euploidy rates (aOR, 0.29; 95% CI, 0.21 to 0.41; p<0.001). Among morphological parameters, only TE grade significantly predicted ploidy, with TE grade C linked to elevated aneuploidy risk (aOR, 3.06; 95% CI, 1.42 to 6.10; p<0.01). Faster blastocyst expansion was correlated with male sex (aOR, 0.95; 95% CI, 0.91 to 0.99; p=0.03). Segmental and whole-chromosomal abnormalities were exclusively age-related.

Maternal age and TE grade are strong predictors of blastocyst ploidy, and expansion speed is associated with sex. These findings support improved embryo selection strategies to promote successful IVF.