How Effective?

One of the most effective methods but carries a small risk of failure:

• Where men cannot have their semen examined 3 months after the procedure to see if it still contains sperm, pregnancy rates are about 2 to 3 per 100 women over the first year after their partners have had a vasectomy. This means that 97 to 98 of every 100 women whose partners have had vasectomies will not become pregnant.
• Where men can have their semen examined after vasectomy, less than 1 pregnancy per 100 women over the first year after their partners have had vasectomies (2 per 1,000). This means that 998 of every 1,000 women whose partners have had vasectomies will not become pregnant.
• Vasectomy is not fully effective for 3 months after the procedure.
  • Some pregnancies occur within the first year because the couple does not use condoms or another effective method consistently and correctly in the first 3 months, before the vasectomy is fully effective.
• A small risk of pregnancy remains beyond the first year after the vasectomy and until the man's partner reaches menopause.
  • Over 3 years of use: About 4 pregnancies per 100 women
• If the partner of a man who has had a vasectomy becomes pregnant, it may be because:
  • The couple did not always use another method during the first 3 months after the procedure
  • The provider made a mistake
  • The cut ends of the vas deferens grew back together

Fertility does not return because vasectomy generally cannot be stopped or reversed. The procedure is intended to be permanent. Reversal surgery is difficult, expensive, and not available in most areas. When performed, reversal surgery often does not lead to pregnancy (see Question 7).

Protection against sexually transmitted infections (STIs): None.

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