There is some evidence that varicoceles might reduce men’s fertility. But scientists do not yet fully understand why that may be. Some experts believe that the quality of the sperm is poorer because the varicocele reduces the blood supply to the affected testicle. Others believe that the build-up of blood in the scrotum raises the temperature of the testicle, which could affect sperm production. If men with a palpable varicocele and poor sperm quality have treatment, the chances of their partner becoming pregnant could possibly improve.