Correlation between quantitative antibody titers of sperm immobilizing antibodies and pregnancy rates by treatments

Immunological infertility in women who possessed sperm immobilizing (SI) antibodies made it very difficult to conceive using the usual treatments. We examined SI antibodies by the quantitative Sperm Immobilization Test and found the antibody titers (50% sperm immobilization unit: SI50 unit) associated with pregnancy rates. Patients with high SI50 titers (>10 units) did not conceive by ordinary or repeated artificial inseminations with husband’s semen (AIH) except when treated with in vitro fertilization (IVF) and embryo replacement. Patients with relatively low SI50 titers (