The aim of this study was to investigate the effect of passive immunotherapy using intravenous immunoglobulin (IVIG) on unexplained recurrent spontaneous abortion (RSA). Live birth rates were analysed and binary data were calculated using risk ratio and 95% confidence interval. Meta-analysis of 11 studies showed that the difference in the live birth rate between the IVIG treatment and placebo groups
was on the margin of significance (RR = 1.25, 95% CI 1.00 to 1.56, P = 0.05). Both cumulative and trial sequential meta-analyses indicated potential beneficial effect of IVIG but the evidence was inconclusive. Subgroup analysis showed that the live birth rate in primary (RR = 0.88, 95% CI 0.71 to 1.07) and secondary (RR = 1.26, 95% CI 0.99 to 1.61) RSA patients was not significantly different between the IVIG and placebo groups. Live birth rate was significantly different when IVIG was administered before conception (RR = 1.67, 95% CI 1.30 to 2.14, P < 0.0001) but not after implantation (RR = 1.10, 95% CI 0.93 to 1.29). Evidence is insufficient to support the beneficial effects of IVIG on an unexplained RSA. Further high quality studies are needed to elucidate the effectiveness of IVIG.