The effectiveness of allogeneic leukocyte immunization in unexplained primary recurrent spontaneous abortion. Recurrent Miscarriage Immunotherapy Trialists Group.

PROBLEM: Unexplained primary recurrent spontaneous abortion (RSA) can be viewed as a partner-specific problem for which immunization with allogeneic leukocytes is being offered as therapy. Published data from randomized controlled trials have produced conflicting results regarding treatment effectiveness. The aim of this study was to perform a subgroup analysis of the data from a recent worldwide collaborative meta-analysis using the raw data for patients with primary RSA entered into randomized controlled trials of immunotherapy. METHODS: Data from randomized controlled trials in eight centers were included in this analysis. Individual patients were included only if they had had three or more spontaneous abortions, no previous pregnancy beyond 20 weeks' gestation, no identifiable cause for the abortions, and no evidence of antipaternal antibodies. Meta-analysis by centre and logistic regression analysis were performed to determine the overall effect of treatment in achieving live birth and to identify variables that affect the prognosis for a successful outcome. RESULTS: In the meta-analysis by center, immunotherapy significantly improved the live birth rate (common odds ratio = 1.94, 95% confidence interval (CI) = 1.20 to 3.12). In the analysis by patient, the likelihood of a successful outcome was also significantly better with treatment (relative risk = 1.46, 95% CI 1.19 to 1.69). The absolute treatment effect was 16.3% producing a number needed to treat of 6. The number of previous abortions had a significant negative correlation with live birth rate, such that for each additional pregnancy loss beyond three, the likelihood of live birth was reduced by 23%. CONCLUSION: Allogeneic leukocyte immunization is an effective treatment for unexplained primary RSA when pretreatment antipaternal antibodies are absent. Better diagnostic tests are required to identify patients who may derive maximal benefit from this therapeutic approach.