PATIENT FACT SHEET from ASRM (American Society for Reproductive Medicine)
Sperm Shape (Morphology): Does It Affect Fertility?
How do doctors decide if a man might have a fertility
For many years, experts have focused on semen analysis, but research studies show that the number of sperm (count) and the movement of sperm (motility) do not always predict fertility very well by themselves.
It may also be useful to look at the shape of the sperm (morphology),
which is also one of the important parts of the semen evaluation.
An updated way of determining sperm shape is called the
Kruger's strict morphology method. Kruger morphology is
a useful system that helps doctors determine if a sperm is
normally shaped or not. It was originally used to predict
the success of in vitro fertilization (IVF), a fertility treatment
in which the sperm are mixed with the woman's egg
in a laboratory.
More recently, it has been used to tell if
intracytoplasmic sperm injection (ICSI) is a necessary
treatment. ICSI is a procedure that helps a sperm fertilize
an egg by injecting a single sperm directly into the center
of the egg.
Even though it is used for these purposes, not all physicians
and scientists are sure that strict morphology method alone
predicts success with IVF or whether it indicates the need
Characteristics of normal sperm
A normal sperm has:
• a smooth, oval shaped head that is 5-6 micrometers long
and 2.5-3.5 micrometers around (less than the size of a
• a well defined cap (acrosome) that covers 40% to 70% of
the sperm head
• no visible defect of neck, midpiece, or tail
• no fluid droplets in the sperm head that are bigger than
one-half of the sperm head size
Intercourse versus artificial insemination
For patients with fertility problems, sperm morphology may have an effect on your ability to achieve a pregnancy. If the strict sperm morphology is more than 4%, there may be little difference in success whether timed intercourse or artificial insemination is utilized.
A successful pregnancy using IVF depends on many of
factors: how many eggs are fertilized, whether the fertilized
eggs grow into embryos, and whether the embryo implants
in the woman's uterus. When strict morphology is 4% or
less, eggs may have a better chance of fertilization with the
use of ICSI.
Frequently asked questions
If an abnormally shaped sperm fertilizes the egg, does
that mean that my child will have genetic abnormalities?
There's no scientific link between the shape of a sperm and
its chromosomal content. Once the sperm penetrates the
egg, fertilization has a good chance of taking place.
However, there may be some male offspring who will
inherit the same type of morphology abnormalities.
Whether routine investigation of Y-chromosome abnormalities
should be initiated when low morphology is noted is
Are there any substances that I can reduce or eliminate
exposure to (e.g., alcohol, tobacco, caffeine) in order to
improve the shape of my sperm?
Studies haven't shown a clear link between abnormal sperm
shape and these factors, but it's a good idea to try to eliminate
use of tobacco and recreational drugs and limit your
consumption of alcohol. These substances reduce sperm
production and function in several ways. They may hurt
sperm DNA (material that carries your genes) quality.
Studies have not shown a clear link between caffeine consumption
and changes in sperm shape.
Are there any dietary supplements or vitamins that I
can take to improve morphology?
Dietary supplements or vitamins have not been clearly
shown to improve sperm morphology. Some specialists do
recommend that you take a daily multivitamin to improve a
number of body functions, including reproductive health.
The American Society for Reproductive Medicine grants permission to photocopy this fact sheet and distribute it to patients.