How reliable is a vasectomy?
Whilst a vasectomy is probably the safest form of permanent contraception, you will not be sterile immediately; for most it takes a minimum of 8-12 weeks for the sperm stored in the seminal vesicle (which is above the site of the vasectomy) to be cleared from the system. After 12 weeks a sperm count is performed which involves taking a specimen of your semen to a pathology centre where it will be sent away to be examined for the presence of sperm. When no sperm are found, sterility has been achieved. One in 10 patients still have sperm present and repeat tests are performed monthly until none are left, 99% are clear by 6 months. The overall failure rates quoted are about 1 in 1000 compared with 1 in 250 in women who have tubal ligation. This includes failure to identify and deal with the vasa, an extra vas and early or late spontaneous rejoining of the ends with re-canalisation. Once it has been established that the semen is clear of sperm subsequent failure of the procedure, due to the spontaneous rejoining of one or both vasa is very rare, occurring only in about 1 in 5000 vasectomies.