Sperm morphological abnormalities as indicators of DNA fragmentation and fertilization in ICSI

Purpose To determine the relationship between sperm morphological abnormalities, DNA fragmentation and fertilization rate in intracytoplasmic sperm injection (ICSI). Methods Sperm samples from 20 ICSI cycles were analysed. Morphology was assessed according to strict criteria, and DNA fragmentation was measured by terminal deoxynucleotidyl transferase (TdT)-mediated fluorescein-dUTP nick end labelling (TUNEL) using flow cytometry. Results A negative correlation was found between the percentage of spermatozoa with elongated heads and fertilization rate. There was a significant difference in the amount of morphological abnormalities between sperm samples with low and high degree of DNA fragmentation. The percentages of amorphous heads and overall head abnormalities were significantly higher in sperm samples with elevated degree of DNA fragmentation. No correlation was found between sperm DNA fragmentation and fertilization rate. Conclusions Head abnormalities, especially amorphous heads, are related to elevated degree of DNA fragmentation. Elongated heads, when detected as predominant abnormal form in sperm samples, may affect fertilization in ICSI.