PROBLEM:Autoimmune mechanisms are involved in etiology of female infertility, the medical problem frequently treated by in vitro fertilization (IVF). Controlled ovarian hyperstimulation (COH) with supraphysiological levels of sex hormones is achieved by IVF. METHODS OF STUDY:Anti-human-ovary and eight common autoantibodies [nuclear (ANA-H, ANA-R on human HEp-2 cell line and rodent antigen, respectively), smooth muscle (SMA), parietal cell, thyroid microsomal, mitochondrial, beta2-glycoprotein-I, cardiolipin antibodies] found in IVF patients (n = 129) were analyzed with regard to the number of previous IVF procedures and the age of the patient. The changes in autoimmune reactions caused by the COH were determined. RESULTS:Endometriosis and polycystic ovary syndrome were associated with a higher number of common serum autoantibodies compared with the tubal factor infertility (Proportion test, P < 0.05). ANA-R was associated with unexplained infertility [adjusted odds ratio (aOR) 8.79, P = 0.038]. SMA correlated with endometriosis (aOR 37.29, P = 0.008), male factor infertility (aOR 20.45, P = 0.018) and with the previous IVF procedures (aOR 2.87, P = 0.013). There was an overall decrease in the number of detectible autoantibodies after COH (Proportion test, P < 0.05). CONCLUSION:COH may have a suppressive effect on the humoral immunity by the time of embryo transfer but more conclusive studies are needed.