Nearly half of vasectomy patients don’t go for sperm checks to ensure they are sterile, according to a study published in Contraception and reported by HealthDay News.

Sperm enters the semen through tubes known as the vas deferens. A vasectomy cuts the tubes, causing sterility. Doctors normally ask patients for a semen sample about three months after the operation to make sure there’s no remaining sperm in the tubes and semen.

For the study, researchers examined 214 medical records of men who had vasectomies to determine how sociodemographic factors (age, marital and educational status) might affect follow-up.

The findings showed that 46 percent of the men skipped getting post-vasectomy semen checks, regardless of age and marital status. Men who weren’t college educated, however, were less likely to follow up.

For a vasectomy to be effective, docs want to see a sperm count of zero after three months, said John K. Amory, MD, an associate professor of medicine at the University of Washington Medical School.

Amory explained that men usually have to ejaculate 20 to 30 times to totally clear sperm from their tubes. This is because the body has to clear millions of sperm, which can live for weeks.

Researchers discussed new strategies to get vasectomy patients to return for sperm checks. Some suggestions include docs making immediate post-op appointments with patients and providing them with home semen analysis tests to measure their sperm count.

Amory called vasectomy a “ pretty darned good” form of birth control that is “about 99 percent effective.”

Read about other male contraception options here.