OBJECTIVETo explore the effects of interventions given to improve pregnancy outcome in women with antiphospholipid antibodies.DATA SOURCESCochrane Controlled Trials Register, Cochrane Collaboration Pregnancy and Childbirth Group's Specialized Register of Controlled Trials, EMBASE, and MEDLINE were searched in December 1999.STUDY SELECTIONRandomized or quasi-randomized controlled trials of therapy for pregnancy loss associated with antiphospholipid antibodies were identified.TABULATION, INTEGRATION, AND RESULTSTrial selection, data extraction, and quality assessment were performed by two authors independently. Quantitative analysis of summary data was performed using the fixed- and random-effects models with heterogeneity assessments. Pregnancy loss and adverse neonatal outcomes were the main outcome measures. Ten trials (n= 627) fulfilled the inclusion criteria (of which four lacked adequate allocation concealment). Three trials of aspirin alone showed no significant reduction in pregnancy loss (relative risk [RR] 1.05, 95% confidence interval [CI] 0.66, 1.68). Heparin combined with aspirin (two trials, 140 patients) significantly reduced pregnancy loss compared with aspirin alone (RR 0.46, 95% CI 0.29, 0.71). Prednisone and aspirin resulted in a significant increase in prematurity (RR 4.83, 95% CI 2.85, 8.21) but no significant reduction in pregnancy loss (RR 0.85, 95% CI 0.53, 1.36).CONCLUSIONCombination therapy with aspirin and heparin may reduce pregnancy loss in women with antiphospholipid antibodies by 54%. Further large, randomized controlled trials with adequate allocation concealment are necessary to exclude significant adverse effects.