Sperm motility describes the ability of sperm to move properly towards an egg. This can also be thought of as the 'quality' of the sperm, which is a factor in successful pregnancies, as opposed to the 'quantity'. Sperm which do not properly 'swim' will not reach the egg in order to fertilize it.
Sperm motility is an important factor in semen quality. Insufficient sperm motility is a common cause of subfertility or infertility.
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