Objective This study was undertaken to verify a specific effect of intravenous immunoglobulin on the outcome of pregnancy in patients with a history of recurrent miscarriage as an alternative to immunotherapy with allogeneic leucocytes.

Study design In a randomised double-blind multicentre study 64 patients with a history of unexplained primary recurrent miscarriage were treated with intravenous immunoglobulin (verum) or 5% human albumin (placebo) infusions during their following pregnancy.

Results Success rates for both verum and placebo, were compared excluding seven patients with explained miscarriage (20/27 (74%) versus 21/30 (70%)) and without any such exclusion (20/33 (61%) versus 21/31 (68%)). The difference between the two groups was not statistically significant.

Conclusions A specific effect of intravenous immunoglobulin in primary recurrent miscarriage could not be demonstrated. These results imply the possibility of psychological influence, i.e. a placebo effect of intravenous immunoglobulin, on the outcome of pregnancy. Since success rates for both verum and placebo were in the same range as for treatment with allogeneic leucocytes, psychological effects might be responsible also for other kinds of immunotherapy for prevention of recurrent miscarriage. However, it cannot be excluded that success rates only reflect background values as reported for recurrent miscarriage patients without any treatment.