Influence of paternal factors on embryo morphokinetics and ART outcomes: a systematic review and meta-regression analysis

Despite growing evidence, the contribution of paternal factors to embryo morphokinetics and clinical outcomes in assisted reproductive technology (ART) has been largely overlooked. This systematic review and meta-analysis was conducted to evaluate associations between sperm parameters and embryo morphokinetic events, and to assess their impact on ART outcomes. Studies published between January 2015 and December 2024 were screened in accordance with the PRISMA guidelines. Morphokinetic variables and clinical outcomes were extracted, and random-effects meta-regression was performed to examine the influence of sperm quality on embryo development and clinical endpoints. Nine studies with heterogeneous case-control definitions and 26,111 embryos (8144 cases versus 17,967 controls) met the inclusion criteria. In study-level meta-analysis and meta-regression, early cleavage events were not significantly associated with sperm quality, whereas lower sperm concentration and motility were associated with delays in later developmental stages. The meta-regression showed that sperm motility was positively associated with implantation (β = 0.035, 95% CI 0.014-0.056; P = 0.0012) and live birth (β = 0.041, 95% CI 0.004-0.080; P = 0.031), while sperm concentration was associated with implantation alone (β = 0.025, 95% CI 0.016-0.034; P < 0.001). No significant associations were observed for fertilization, clinical pregnancy or miscarriage. These findings provide meta-analytic evidence linking paternal sperm quality to embryo morphokinetics, and underscore the importance of considering paternal factors in ART outcomes.