Antibodies are often thought of only as mechanisms that help the body prevent infection. When the body recognizes a ‘foreign’ substance, it tries to build up immunity or antibodies against that substance. But in the case of anti-sperm antibodies, the body recognizes the sperm as foreign and antibodies build up against the sperm, working against the body and interfering with the reproductive process. In women, antibodies (when present) can inhibit sperm movement as they make their way through the woman’s cervical mucous in an effort to reach an egg. In men, antibodies on the sperm’s tail may also impair the sperm’s movement through the woman’s mucous.

The reasons why these antibodies develop may be due to infections or other factors. To check for the presence of anti-sperm antibodies, healthcare providers might run an immunobead test (IBT).