The presence of Anti-sperm antibodies (ASA) in the semen can reduce the chances of natural conception. Antibodies can cross from the blood into the semen if the blood-testis barrier is breached. There are a number of reasons why this can occur. Unfortunately high levels of anti-sperm antibodies can affect sperm motility and may affect transit of sperm through the female reproductive tract. The antibodies in high concentrations can impact on the process of egg fertilisation too. The laboratory technique of ICSI is advised in cases where high levels of ASA are noted on sperm analysis. Taking steroids to suppress these antibodies has not been shown to be effective at improving pregnancy rates.