Worldwide Collaborative Observational Study and Meta‐Analysis on Allogenic Leukocyte Immunotherapy for Recurrent Spontaneous Abortion¹

PROBLEM: Recurrent spontaneous abortion (RSA) is a common complication of pregnancy for which there is no known cure. Therefore, effective treatment is needed. Published results from controlled clinical trials of allogeneic leukocyte immunization of women suffering from RSA have given conflicting results. To address this controversy, the international raw data of all patients who had been entered into clinical trials that included a control group were collected and analyzed. The primary question to be answered was whether alloimmune stimulation of the female partner improves the subsequent live birth rate. METHODS: Fifteen clinical centers were identified worldwide because they controlled appropriate raw data. Consequently, nine randomized trials (seven double‐blinded) were evaluated independently by two separate data analysis teams to assure conclusions were robust. One team also compared randomized trials to the results of six nonrandomized cohort‐controlled studies to test for bias in nonrandomized trials. Factors predicting successful live births among couples with RSA were evaluated by logistic regression. RESULTS: Although the two independent analyses made use of different definitions and utilized different statistical methods, the results of both were similar. The live birth ratios (ratio of live births in treatment and control groups) with 95% confidence intervals (CI) were 1.16 (CI, 1.01‐1.34, P = 0.031) and 1.21 (CI, 1.04‐1.37, P = 0.024), respectively. The absolute differences in live birth rates between treatment and control groups were 8% and 10% in respective analyses. Results in randomized and nonrandomized trials were surprisingly similar despite significant differences in composition of control and treatment groups. Live birth rates were lower with older female partners, more than five abortions, with a positive ANA or with positive anticardiolipin antibodies. Live birth rates were higher if the female partner had prior to treatment serum antibodies to paternal leukocytes or converted from negative to positive with immunization. Approximately 0.5% of controls and 2.1% of treated patients experience side effects for a 1.6% treatment related effect. There was no evidence of an increased risk of adverse effects on the fetus. CONCLUSIONS: Two independent analyses of worldwide data on allogeneic leukocyte immunization for treatment of RSA suggest that alloimmunization may be an effective treatment. The treatment effect appears, however, to be small, and the data indicate that immunotherapy helps only 8% to 10% of affected couples. A current lack of diagnostic tests defining patients who most likely would benefit from immunotherapy, precludes the identification of a patient population that would benefit most from such treatment. The efficacy of treatment in such a subgroup could be expected to increase and could be of sufficient magnitude to allow the determination of more effective immunization protocols. This study does not exclude the possibility of a partial correction of a widely prevalent immunology defect by immunotherapy. The presence of such a defect would indicate a need for more effective therapy. The unexplained variation in pregnancy success rates of control groups among centers continues to present a statistical problem, limiting the statistical evaluation of retroactively obtained data.