Vasectomy is a permanent method of birth control for men that prevents sperm from leaving the body to start a pregnancy. Compared to female sterilization, vasectomy is cheaper, easier and involves minimal recovery. Although vasectomy is highly effective, it does not stop the testes from making sperm, so in the rare cases when a vasectomy fails, the man is still fertile.
Procedure
In a vasectomy, the surgeon cuts through the tubular vas deferens leading from each testicle and seals the ends using surgical clamps, ties or heat. With the vas deferens blocked, the testes still make sperm but they cannot leave the body and are harmlessly re-absorbed. After a vasectomy, the volume of ejaculate does not change because downstream of the vas deferens the male tract continues to make semen, the fluid that normally bathes the sperm.
Timing
According to the Mayo Clinic, vasectomy is almost 100 percent effective for birth control. However, vasectomy does not immediately make a man sterile. A vasectomy can "fail" if the man has unprotected sex too soon after the procedure, when fertile sperm still remain. Sperm stored in a widened area of the vas deferens called the ampulla remain after a vasectomy and can start a pregnancy. Planned Parenthood advises that a man should not consider himself sterile until a semen analysis shows no sperm in the ejaculate. Most doctors recommend semen analysis at eight to 12 weeks following the procedure, according to Dr. Labrecque, writing in the May 2005 issue of "Fertility and Sterility."
Recanalization
Recanalization occurs when the severed ends of the vas deferens spontaneously grow back together, allowing sperm to move through the male reproductive tract. When semen analysis shows motile sperm---those able to swim and fertilize an egg---in the ejaculate after about eight to 12 weeks following the procedure, doctors suspect recanalization. Planned Parenthood cites a frequency of about 1 in 2,000 cases, but other studies, as cited by Dr. Labrecque, range from 0.3 percent to 13 percent. Dr. Labrecque also reports that some cases of early recanalization will subsequently scar over to block the tubes, resulting in "delayed vasectomy success."
Other Causes
Surgical errors---for example if the surgeon accidentally cuts the same vas deferens in two places instead of cutting the vas deferens from each testicle---can cause vasectomy failure. In very rare cases, a man might have a duplicated vas deferens, so that when the surgeon cuts one vas deferens from each testicle, another viable but undetected vas deferens still remains.
Other Causes
Dr. Labrecque found that the likelihood of vasectomy failure varied with the method that the surgeon used to seal off the ends of the vas deferens. When the surgeon used clips to seal off the ends, about 10 percent of men were still fertile eight to 12 weeks later, as compared to only 0.5 percent when the surgeon used heat to cauterize the ends and interposed a natural tissue barrier at the sealed ends further from the testes.
References
- Mayo Clinic.com: Vasectomy
- Planned Parenthood: Vasectomy
- "Delayed vasectomy success in men with a first postvasectomy semen analysis showing motile sperm"; Michel Labrecque, Karine St. Hilaire and Lucile Turcot; May 2005 Fertility and Sterility.
