Sperm Motility

What It Means, What's Normal, What's Not

Microscopic image of sperm
In order for fertilization to occur, sperm must swim to the ovulated egg.. De Agostini Picture Library / Getty Images

Quick Definition:

Sperm motility refers to the movement and swimming of sperm.

Poor sperm motility means that the sperm do not swim properly, which can lead to male infertility. Poor sperm motility is also known as asthenozoospermia.

Why Do Sperm Swim?

Sperm are motile cells. This means that they are cells that make themselves move. This is important when it comes to getting pregnant.

Usually, when a man and woman have vaginal sexual intercourse, the man will ejaculate semen near the cervical canal, at the end of the vaginal canal.

While this is where you want the semen to be if you're trying to get pregnant, any semen ejaculated near the vaginal area can technically make it's way up the vaginal canal and to the cervix.

Semen can also get into the vaginal canal without ejaculation, from what is known as pre-ejaculate. This is a small amount of semen like fluid that comes out of the urethra when a man is sexually aroused. (This is why the "pull out method" doesn't work to prevent pregnancy.) 

Sperm are programmed to swim in a way that will hopefully reach their ultimate destination: the ovulated egg.

While the egg is moved along from the ovary into the fallopian tube by tiny hair like projections called cilia, the egg itself doesn't swim. It is more or less floats its way into and through the fallopian tubes with the help of the cilia.

Sperm, on the other hand, move themselves. They must swim up from the cervical canal, into and through the uterus, and, eventually, into the fallopian tube.

This is where they will hopefully meet up with an ovulated egg.

Once there, the sperm must fertilize the egg, which also requires movement.

Progressive Motility, Non-Progressive Motility, and Total Motility

Progressive motility refers to sperm that are swimming in a mostly straight line or in very large circles.

Non-progressive motility refers to sperm that move but don't make forward progression or swim in very tight circles.

For example, a sperm that just vibrates in place would be considered non-progressive. A sperm that zigzags but makes forward progression would be considered progressive.

Progressive motility is needed in order for the sperm to swim their way up the female reproductive tract.

Total motility refers to the percentage of sperm making any sort of movement. This movement can include non-progressive movement.

How Many Sperm Must Swim Properly

In a man with normal fertility, one ejaculate of semen may contain over 39 million sperm. Not all of those sperm, however, are expected to be completely healthy.

When it comes to sperm motility, for an ejaculate sample to be considered normal, at least 40% of the sperm should be motile, or moving. This can include non-progressive movement.

At least 32% of the sperm should show progressive motility.

What Affects Sperm Motility

Sperm motility can be affected by a number of things.

Usually, when sperm motility is poor, there are other problems found with sperm health.

For example, men with poor sperm motility may also have low sperm counts or poor sperm morphology (or sperm shape.) Sperm that aren't formed properly can't swim properly.

Sperm motility may be harmed by exposure to chemicals, illness, exposure to heat or cold, bad health habits like smoking, or abnormalities of the male reproductive tract, like with a varicocele.

Poor sperm motility may also occur if a man has infrequent sexual activity. In this case, if the first ejaculate collected showed poor motility, a second ejaculate collected soon after should be better.

More on male fertility:

Sources:

Rouge, Melissa. Sperm motility. http://www.vivo.colostate.edu/hbooks/pathphys/reprod/semeneval/motility.html

WHO Laboratory Manual for the Examination and Processing of Human Sperm. Fifth Edition. http://whqlibdoc.who.int/publications/2010/9789241547789_eng.pdf

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