Semen parameters on the day of fertilization and PGT-A outcomes in couples with idiopathic early recurrent pregnancy loss

The association between semen parameters on the day of fertilization and preimplantation genetic testing for aneuploidy (PGT-A) outcomes in couples with idiopathic early recurrent pregnancy loss (RPL) remains uncertain. This retrospective cohort study included 998 couples with idiopathic early RPL who underwent their first next-generation sequencing-based PGT-A cycle between January 2017 and December 2022, yielding 4352 biopsied blastocysts. Semen volume, sperm concentration, and total motility were assessed on the day of intracytoplasmic sperm injection according to World Health Organization sixth-edition thresholds. Embryo-level associations were analyzed using generalized estimating equations, and clinical outcomes after single euploid frozen-thawed embryo transfer were evaluated using multivariable logistic regression. Lower sperm concentration (<16 × 106/mL) was not significantly associated with embryo aneuploidy but was associated with increased odds of embryo mosaicism in the adjusted model (adjusted odds ratio [aOR] 1.437, 95% confidence interval [CI] 1.108–1.864; p = 0.006). This association remained significant in the multivariable model (OR 1.432, 95% CI 1.084–1.892; p = 0.012). Semen volume <1.4 mL and total motility <42% were not significantly associated with embryo aneuploidy or mosaicism. In analyses of reproductive outcomes after single euploid embryo transfer, semen volume, sperm concentration, and total motility were not significantly associated with live birth or total pregnancy loss. These findings suggest that reduced sperm concentration on the day of fertilization may be associated with embryo mosaicism in couples with idiopathic early RPL undergoing PGT-A, whereas conventional semen parameters do not appear to compromise live birth or pregnancy loss outcomes once a euploid embryo is transferred.