One year after vasectomy, the cumulative probability of failure per 1,000 vasectomy procedures was 9.4.

According to the U.S. Collaborative Review of Sterilization (CREST) Working Group, among a group of 540 women aged 18 to 44 whose husbands underwent vasectomy, 6 became pregnant 6 to 72 weeks after vasectomy.

Half of the failures occurred within 3 months of vasectomy, when "most providers" advise couples to use back-up contraception or refrain from intercourse, Dr. Denise J. Jamieson from the Centers for Disease Control and Prevention in Atlanta and colleagues note. However, 2 pregnancies occurred more than 12 months after vasectomy.

Two, three, and five years after vasectomy, the cumulative probability of failure per 1,000 procedures was 11.3.

The 5-year failure rates following vasectomy are "similar to those previously reported following tubal sterilization and similar to vasectomy failure rates previously reported in 2 other studies," the authors note.

"Couples who are considering sterilization should be counseled that both male and female sterilization are highly effective methods of permanent contraception but that pregnancies can occur," they suggest.

Couples should also be made aware that men are not sterile immediately after the procedure and, "until the absence of sperm is documented on microscopic examination of the semen (where semen analysis is available), intercourse should be avoided or another method of contraception should be used."

Obstet Gynecol 2004;103:848-850.

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