These Y-shaped molecules take on an important role in the body. They help the body defend itself from bacteria and viruses by recognizing and binding to very small structures on their surfaces. The antibodies can be responsible for an inability to conceive if they are found in the mucus that is formed in the uterine neck prior to ovulation (the so called cervical mucus). This mucus is viscous and thready several days before ovulation. Some women use these signs to identify their fertile days.
The presence of sperm-targeting antibodies in the cervical mucus can be a reason why some couples may be unable to achieve pregnancy.