Mayo Clinic: Men’s Health Center


Y Chromosome Microdeletion (YCM), is a common genetic cause of male infertility. It is caused by the genetic re-shuffling of the Y chromosome (the male chromosome). When certain portions of the Y chromosome are missing, men will typically not have any symptoms other than infertility. The impact this can have on infertility ranges from a minimal effect on sperm counts, to completing stopping sperm production.

It is estimated that approximately 1 in every 2,000 men have detectable deletions on the Y chromosome that can impact fertility, but as many as 15% of men who are diagnosed with infertility will have YCM.

Most of the time, the only impact by YCM is sperm production. Sometimes the body will try to compensate for poor sperm production increasing hormone signaling to the testicle.

In addition to the fertility implications for men who test positive for YCM, they should consider meeting with a medical geneticist or genetic counselor prior to having children to discus the risk of passing a YCM to their children.

Why it's done

A YCM test should be performed in men with unexplained infertility who have a semen analysis that shows very low sperm production (defined as less than 5 million sperm) or no sperm (called azoospermia). This test may guide treatment options for fertility in men who test positive for YCM.


A YCM test generally has little physical risk. When the needle is inserted to draw blood, some people may feel some pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise.

A YCM test can have emotional, social and financial risks as well. Discuss all risks and benefits of genetic testing with your doctor, a medical geneticist or a genetic counselor before you have a genetic test.

How to prepare

YCM test is a blood test. You do not need to be fasting when the labs are drawn, but you may want to discuss the implications of testing with a medical geneticist or genetic counselor prior to testing.


CM tests look for the most common abnormalities in the Y chromosome that can lead to infertility, but may not detect rare forms of the genetic abnormality. The three most common abnormalities and their implications on fertility are as follows:

  • Y chromosome microdeletion AZFa: Infertile, no sperm production
  • Y chromosome microdeletion AZFb: Infertile, no sperm production
  • Y chromosome microdeletion AZFc: May be fertile, sperm production may be present

A Y chromosome microdeletion in the AZFc region does not guarantee that sperm production will be present, but instead means that sperm production may be present.

Did you know?

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