Antibodies can be present in the cervical mucus which are directed against the sperm cells and make them immotile. This can be an obstacle for the sperm cells on their way to the egg.

The Kremer test can be used to find out whether these antibodies are present. A prerequisite for carrying out the Kremer test is a normal condition of the cervical mucus and a spermiogram with good motility and concentration of the sperm cells.