April 7, 2006 -- A vasectomy can take months to take full effect, but many men skip follow-up tests that check the vasectomy's success, a new study shows.

A vasectomy is a permanent sterilization procedure for men. Doctors cut the vas deferens, which are tubes in the male reproductive system that carry sperm. A vasectomy prevents sperm from being transported out of the testes, but it doesn't affect a man's orgasm or ejaculation. It also doesn't prevent sexually transmitted diseases.

While vasectomy almost always works, success isn't necessarily instant. That's why doctors ask men to get follow-up tests. Until those tests show success, patients and their female partners need to use another form of birth control to avoid pregnancy.

No Clue About Success

The new study, published in BJU International, included 436 men who got vasectomies at The Cleveland Clinic.

The men were told to submit two semen samples two months after vasectomy and again a month later. If those samples contained sperm, the men were to submit semen samples monthly until they had gotten two consecutive negative tests.

A quarter of the men didn't do their two-month test, and only 21% followed the full instructions to get two back-to-back negative tests, the study shows.

The no-shows for the two-month test "had no idea whether the procedure was successful or if their partner could still become pregnant," researcher Nivedita Dhar, MD, says in a news release. Dhar is the chief urology resident of The Cleveland Clinic's Glickman Urological Institute.

Patients' Results

In patients who followed the testing rules, vasectomy was eventually judged successful in all but one man, the study shows.

Two months after vasectomy, sperm were found in a quarter of the semen samples that were submitted. Most of those sperm were rare and nonmotile, meaning they were few in number and couldn't move on their own.

But three samples showed rare motile sperm, which can move. A man who submitted one of those samples later got a second vasectomy, which worked.

Three months after vasectomy, half of all patients submitted semen samples, 9% of which contained sperm. Three patients whose semen samples showed no sperm at two months showed rare, nonmotile sperm in the three-month check. Those three men all had sperm-free semen samples four and five months after vasectomy.

It's "impossible," Dhar says, to know if and when the vasectomies succeeded in the patients who didn't submit semen samples.

Fewer Tests, Better Compliance?

Dhar and colleagues suggest simplifying the follow-up process to encourage more men to get follow-up tests after vasectomy.

"Provided patients have been adequately counseled, we think that one negative semen analysis at three months or one with rare, nonmotile sperm at two months may be adequate to determine the success of vasectomy," the researchers write.

SOURCES: Dhar, N. BJU International, April 2006; vol 97: pp 773-76. WebMD Medical Reference provided in collaboration with The Cleveland Clinic: "Sexual Health: Your Guide to Birth Control: Sterilization." News release, The Cleveland Clinic.

Reviewed by Louise Chang