Several head shapes and sizes have been described by the WHO (1999, 2010).
|Normal||regular oval shape|
|Macrocephalic||the head is clearly above the normal|
|Microcephalic||the head is present but clearly smaller than the normal size|
|Elongated||the head has the form of a cigar|
|Pyriform||the head has the form of a pear|
|Amorphous||the head has slight to strong deviation from oval form|
|Double||two heads attached to one or two midpieces and tails|
|Pin||the head is absent, but the cells are alive and usually move|
|Round||the head is perfectly spheric and no acrosome is present|
Presence of vacuoles
The presence 1-2 vacuoles in the sperm head can be considered as normal. More than 2, should be considered as abnormal, according to the strict criteria.