Fragmentation of DNA in morphologically normal human spermatozoa.

OBJECTIVE To evaluate DNA fragmentation in spermatozoa with normal morphological appearance. DESIGN Prospective study. SETTING Academic tertiary center. PATIENT(S) Fertile, subfertile, and infertile men were studied. INTERVENTION(S) Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-fluorescein nick-end labeling assay and morphology assessment by phase contrast in the swim-up fractions. MAIN OUTCOME MEASURE(S) Simultaneous assessment of the percentage of normally shaped sperm and DNA fragmentation. RESULT(S) No DNA fragmentation was found in spermatozoa with normal morphology in any of the samples from the fertile group. In only one sample from the subfertile group did we observed normally shaped sperm cells exhibiting DNA fragmentation. However, in all the samples from the infertile group, we observed normal spermatozoa with DNA fragmentation. Spermatozoa from this late group exhibited a high proportion of DNA damage. CONCLUSION(S) In infertile men with moderate and severe teratozoospermia, the spermatozoa with apparently normal morphology present in the motile fractions after swim-up may have DNA fragmentation.