Infertility - Immunological problems
In some partners, the female will develop an immunological response to the male's semen. This means that her immune system attacks the sperm, responding the same way it would to an invasion by a virus. The immune system destroys the sperm before it can reach the ovum. Why this occurs is unknown, but the response fades if exposure to the sperm is eliminated. The treatment for immunological attacks is eliminating intercourse or using condoms for several months until the female's immune system shuts off the mechanism that responds to the sperm.