Inner Cell Mass Grade and Earlier Blastulation Are Associated with Pregnancy Outcomes in Euploid Embryos.

To assess the relationship between blastulation, ICM (inner cell mass) quality, TE (trophectoderm) quality, embryo sex, or embryo sex selection and live birth among euploid embryos. Single-center retrospective cohort analysis of patients who underwent single frozen embryo transfer (FET) following autologous IVF with preimplantation genetic testing for aneuploidy from 2020-2021. Blastocysts underwent trophectoderm biopsy with ICM and TE grading before vitrification. The associations between live birth (LB) and patient/embryo characteristics were assessed with mixed-effect multivariable logistic regression. In 768 euploid FET cycles with available live birth data, 404 cycles (52.6%) resulted in live birth. A significantly lower odds of LB was seen with vitrification on days 6 and 7 compared to day 5 (aOR 0.81, 95% CI 0.70-0.95) and in embryos with lower ICM quality compared to those with quality 1, the highest of three quality grades and indicative of tightly packed cells (aOR 0.75, 0.62-0.90). Embryo sex was known in > 90% of transferred embryos, with 355 (50.8%) female and 344 (49.2%) male. In 161 (21.0%) cycles where embryo sex was used to select embryo for transfer with 84 (52.2%) male and 77 (47.8%) female, embryo sex and embryo sex selection were not significantly associated with the odds of LB. Prioritizing embryos for transfer with better ICM quality and earlier blastulation may provide the highest chance of LB. Trophoblast quality at vitrification, embryo sex, and embryo sex selection were not associated with the odds of LB, but these factors may influence patient and physician decision-making.