Though vasectomy is considered to be a permanent form of birth control for men, approximately 1 in 2000 men conceive children, following vasectomy. There are two primary reasons for this:
- There were still live sperm in the semen
- Failed procedure due to spontaneous reconnection of the vas deferens tube
There may be sperm in the semen for several months following a vasectomy. Many people believe that as soon as they are well enough to resume sexual activity that they are also unable to conceive, however it takes the body some time to clear the semen of active sperm - usually 15 to 20 ejaculations. Men will need to utilize other methods of contraception until their sperm count is zero, which can take up to 8 months.
Though it is uncommon, the vas deferens may reconnect themselves, following a vasectomy. This is called "recanalization" and is more common with procedures where a significant length of the tube was not removed. For best results, surgeons should remove a length of the vas, or cauterize the ends, to prevent recanalization and subsequent birth control failure.
