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How is a man tested for infertility?
The most common test of a man’s fertility is a semen
analysis. This measures many features of the sperm
and semen (the fluid in which the sperm are contained).
The most important of these are the number of sperm
(sperm count), motility of the sperm (percentage of
moving sperm), morphology of the sperm (percentage
of normally shaped sperm), and the volume of fluid.
How is morphology assessed?
To assess sperm morphology, the sperm are examined
under a microscope and the percentage of abnormally
shaped sperm is estimated. It is important to know
that all men produce abnormal sperm and as many
as half of the sperm in a “normal” semen sample are
Sperm morphology is assessed using one of 2 sets of
characteristics. Kruger criteria are strict and consider
minute irregularities as abnormal. World Health
Organization (WHO) criteria are more lenient and do
not classify as many sperm as abnormal.
In some cases, morphology is used to decide whether
a couple should use in vitro fertilization (IVF) to attempt
a pregnancy. It is best to check with your physician to
see which method was used to assess sperm shape
and the significance of the results.
What is a normal-shaped sperm?
A normal sperm has:
- A smooth, oval-shaped head that is 5-6
micrometers long and 2.5-3.5 micrometers wide
(less than the size of a needle point)
- A well-defined cap (acrosome) that covers 40% to
70% of the sperm head
- No visible abnormality of neck, midpiece, or tail
- No fluid droplets in the sperm head that are bigger
than one half of the sperm head size
Can an abnormally shaped sperm fertilize an egg?
Yes, it can. However, having higher amounts of
abnormally shaped sperm has been associated with
infertility in some studies. Usually, higher numbers of
abnormally shaped sperm are associated with other
irregularities of the semen such as low sperm count or
motility. Men with abnormally shaped sperm may also
have no trouble causing a pregnancy.
If an abnormally shaped sperm fertilizes the egg,
does that mean that my child will have a higher risk
of having genetic abnormalities?
We don’t know. There’s no relationship between the
shape of a sperm and its genetic material. Once the
sperm enters the egg, fertilization has a good chance of
taking place. However, as some of the abnormalities in
sperm shape may be the result of genetic disturbances,
there may be some male offspring who will inherit the
same type of morphology abnormalities as are found in
their fathers’ sperm morphology.
If an abnormally shaped sperm can fertilize an egg,
why does the shape matter?
No one is sure why the sperm shape matters. Men
with abnormally shaped sperm tend to have more
trouble causing a pregnancy, but we cannot say for
sure whether that difficulty is caused by the shape of
the sperm itself or by another reason that causes the
sperm to be shaped differently and at the same time
causes a problem with fertility.
Is there anything I can do to improve the shape of
Research has not shown a clear relationship between
abnormal sperm shape and tobacco, alcohol, or
caffeine use, though some studies suggest that
smoking can impair fertility. While you are trying for a
pregnancy, you should not use tobacco or recreational
drugs and you should limit your consumption of alcohol.
These substances may hurt sperm DNA (material that
carries your genes) quality. Studies have not shown
a clear connection between caffeine consumption
and changes in sperm shape. Remember that it may
take up to 3 months for any changes to your sperm to
Are there any dietary supplements or vitamins that
I can take to improve morphology or fertility?
Dietary supplements or vitamins have not been shown
to improve sperm morphology or fertility. Some
specialists recommend that you take a daily multivitamin
to improve reproductive health even though the value
of dietary multivitamins for this purpose is unproven.
Sperm Shape (Morphology): Does It Affect Fertility?-pdf