Seasonal Variations in Human Semen Parameters: A Systematic Review and Meta-Analysis

Male fertility can be influenced by environmental factors, including seasonal variation, which may cause fluctuations in semen quality. However, studies to date have reported inconsistent findings, limiting our understanding of how seasonality affects reproductive potential. A clearer picture of these patterns is essential for optimizing the timing and interpretation of fertility evaluations.

To systematically review and meta-analyze existing data on seasonal differences in semen analysis parameters.

We searched PubMed, Web of Science, and Scopus up to March 18, 2025 using the key search terms of "semen parameter" and "seasonality," along with their related terms. Initial search yielded 641 studies. The inclusion criteria were original articles or conference abstracts that investigated any human semen parameters across different seasons. After screening, 21 studies were included for meta-analysis. We calculated the pooled weighted mean differences in semen parameters across different seasons using the random-effects models.

Meta-analyses of 21 studies with high methodological quality showed that winter and spring had better semen quality than summer and fall, in that they had higher sperm concentration of 3.24-6.07 million/mL, higher total sperm count of 14.63-19.74 million, and lower slow motility of 5.17%-11.75%. Additionally, winter had greater normal morphology of 1.30% than both fall and summer. Spring also had greater total motile sperm count of 4.34-4.38 million compared with fall and summer and greater normal morphology of 0.88% than summer. Summer had lower slow motility of 5.05% than fall.

This meta-analysis showed seasonal variations in semen parameters, with generally better semen quality in winter and spring compared with summer and fall. Specifically, these seasons were associated with higher sperm concentration, greater total sperm count, and reduced slow motility compared with summer and fall.