A human morphologically normal spermatozoon may have noncondensed chromatin.

According to numerous assisted reproductive medicine practitioners, semen with normal characteristics might not require further investigation. However, on the scale of the individual spermatozoon, it is well known that normal morphology does not guarantee optimal nuclear quality. Here, for 20 patients with normal sperm characteristics and a high proportion of spermatozoa with noncondensed chromatin, we subsequently assessed chromatin condensation status (aniline blue staining) and morphology (Papanicolaou staining) of the same 3749 spermatozoa. Although the overall proportion of morphologically normal spermatozoa was not correlated with the overall proportion of spermatozoa with noncondensed chromatin, an individual spermatozoon's morphology appeared to be closely related to its chromatin condensation status. Morphologically normal spermatozoa with noncondensed chromatin were seen in all patients; the proportion averaged 23.3% [min 10.9%-max 44.4%]. Morphologically abnormal spermatozoa were more likely to have noncondensed chromatin than morphologically normal ones (P < 0.0001). Small-, large- or multiple-headed spermatozoa presented the highest degree of noncondensation (>80% for each type), and more than half the vacuolated spermatozoa also presented noncondensed chromatin. However, a morphologically normal spermatozoon may also have a noncondensed chromatin.