Causes of Male Infertility
Approximately 66% of infertile men have a problem where they make low numbers of sperm and/or sperm that do not work properly.
About one in five infertile men have other physical problems, including those who have had a vasectomy but now want to have children. Blockages (often called obstructions) in the tubes leading from the testicles to the penis can stop some men from ejaculating sperm.
Other less-common causes of male infertility include sexual problems, low levels of hormones made in the brain, and, sometimes, genetics.
The most common genetic causes of infertility are chromosomal conditions that affect the way sperm is produced. These include Klinefelter syndrome (i.e., a condition where you are born with an extra X chromosome), Y chromosome deletions (i.e., a condition where you have genetic material missing from your Y chromosome that is important for sperm production), and other genetic problems, such as Down Syndrome.