The aim of this trial was to investigate whether infusions of i.v. immunoglobulins (Ig) to women with secondary recurrent spontaneous abortions and recurrent second trimester spontaneous abortions can increase the rate of successful pregnancy. In a prospective, double-blind, placebo-controlled trial, infusions of i.v. Ig (Nordimmun) or placebo were given during pregnancy to 34 women with a history of either unexplained recurrent spontaneous abortion subsequent to a birth or including at least one second trimester miscarriage. The success rate was 52.9% in the i.v. Ig group compared with 29.4% in the placebo group (not significantly different, therapeutic gain 23.5%, 95% confidence interval -8.6 to 55.7%). No changes in autoantibody concentrations or major lymphocyte subsets were induced by i.v. Ig treatment. In conclusion, an expected 55% therapeutic gain of i.v. Ig in recurrent spontaneous abortion could not be confirmed using the treatment regimen tested. However, to determine whether the trend of therapeutic gain of i.v. Ig in these women may be statistically significant, a larger trial is in progress.