Teratozoospermia and Embryo Development: The Significance of Sperm Selection in In Vitro Fertilization Success

Background: Sperm morphology is a key factor influencing fertilization and embryo development in assisted reproductive technology (ART). However, the predictive value of sperm deformity indices and selection techniques remains debated. This study evaluated the impact of teratozoospermia on fertilization, blastocyst formation, and embryo quality, comparing conventional and microfluidic sperm selection methods. Methods: A retrospective analysis was conducted on ART cycles involving patients with teratozoospermia. Sperm selection was performed using density gradient centrifugation (DGC) or microfluidic sperm sorting (MFSS). The correlations between the Sperm Deformity Index (SDI), Multiple Anomalies Index (MAI), and Teratozoopermia Index (TZI) with fertilization rates, blastocyst formation, and embryo quality were assessed. Statistical analysis included correlation tests, receiver operating characteristic (ROC) curves, and independent samples t-tests. Results: Patients with severe teratozoospermia exhibited lower fertilization rates (p < 0.01) and reduced blastocyst formation (p = 0.02). The SDI and MAI showed moderate negative correlations with fertilization (r = −0.15 and r = −0.25, respectively) and blastocyst development (r = −0.20 and r = −0.30, respectively), while the TZI had only weak associations (r = −0.10 and r = −0.15, respectively). ROC analysis demonstrated that the SDI and MAI were moderate predictors of embryo viability (AUC = 0.70 and 0.75, respectively). Patients who underwent microfluidic sperm selection had higher fertilization rates (p = 0.03) and improved blastocyst quality (p = 0.04) than those processed with DGC. Conclusions: Severe teratozoospermia negatively affects fertilization and blastocyst formation, with the SDI and MAI showing moderate predictive value for embryo development. The use of microfluidic sperm selection significantly improved embryo quality, supporting its clinical relevance in ART.