A semen analysis evaluates certain characteristics of a male's semen and the sperm contained in the semen. It may be done while investigating a couple's infertility or after a vasectomy to verify that the procedure was successful. It is also used for testing donors for sperm donation, in stud farming and farm animal breeding. Many men, especially if they are older, have a semen quality analysis, testing for common STIs, and perhaps testing for genetic defects done as part of routine pre-pregnancy testing, though this is decisively not the norm, as most doctors will not test the semen and sperm (and the man's genome and his STI status) unless specifically requested or there is a strong suspicion of a pathology in one of these areas discovered during the medical history or during the physical examination...