Hostile cervical mucus may refer to cervical mucus that is thick and sticky around the time of ovulation, instead of wet, raw egg-white like, and stretchy. It may also refer to cervical mucus that is too acidic for sperm survival.
Sometimes, hostile cervical mucus refers to the presence of anti-sperm antibodies. In this situation, the cervical mucus itself may not appear any different to the naked eye than a person without the problem. Anti-sperm antibodies are an immune response, where white blood cells attack the sperm. Anti-sperm antibodies may be produced by the woman's body, or may be present in the man's semen.

