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Updated: Feb 15, 2026
U-Shaped Horizontal Swimming Technique for Preparing High-Quality Sperm with Low DNA Fragmentation Index
Published on: March 28, 2025
Sperm DNA fragmentation and sex chromosome aneuploidy after swim-up versus density gradient centrifugation
Sung Woo Kim1,2, Byung Chul Jee2,3, Seul Ki Kim2,3
1Department of Obstetrics and Gynecology, Seoul National University Hospital, Seoul, Korea.
Objective:
The aim of this study was to compare the efficacy of swim-up and density gradient centrifugation (DGC) for reducing the amount of sperm with fragmented DNA, sex chromosome aneuploidy, and abnormal chromatin structure.
Methods:
Semen samples were obtained from 18 healthy male partners who attended infertility clinics for infertility investigations and were processed with swim-up and DGC. The percentages of sperm cells with fragmented DNA measured by the sperm chromatin dispersion test, normal sex chromosomes assessed by fluorescence in situ hybridization, and abnormal chromatin structure identified by toluidine blue staining were examined.
Results:
The percentage of sperm cells with fragmented DNA was significantly lower in the swim-up fraction (9.7%, p=0.001) than in the unprocessed fraction (27.0%), but not in the DGC fraction (27.8%, p=0.098). The percentage of sperm cells with normal X or Y chromosomes was comparable in the three fractions. The percentage of sperm cells with abnormal chromatin structure significantly decreased after DGC (from 15.7% to 10.3%, p=0.002). The swim-up method also tended to reduce the percentage of sperm cells with abnormal chromatin structure, but the difference was not significant (from 15.7% to 11.6%, p=0.316).
Conclusion:
The swim-up method is superior for enriching genetically competent sperm.
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