Objective This study was designed to evaluate the efficacy and safety of aspirin-heparin treatment for un-explained recurrent spontaneous abortion (URSA). Methods Literatures reporting the studies on the aspirin-heparin treatment of un-explained recurrent miscarriage with randomized controlled trials (RCTs) were collected from the major publication databases. The live birth rate was used as primary indicator, preterm delivery, preeclampsia, intrauterine growth restriction, and adverse reactions (thrombocytopenia ) were used as the secondary indicators. The quality of the included studies was evaluated using RCT bias risk assessment tool in the Cochrane Handbook (v5.1.0). Meta-analysis was conducted using RevMan (v5.3) software. Subgroup analyses were conducted with an appropriately combined model according to the type of the treatments if heterogeneity among the selected studies was detected. Results Six publications of RCTs were included in this study. There were a total of 907 pregnant women with diagnosis of URSA, 367 of them were pooled in the study group with aspirin-heparin therapy and 540 women in the control group with placebo, aspirin or progesterone therapy. Meta-analysis showed that the live birth rate in the study group was significantly different from that in the control group [RR = 1.18, 95% CI (1.00-1.39), P=0.04]. Considering the clinical heterogeneity among the six studies, subgroup analysis were performed. Live birth rates in the aspirin-heparin treated groups and placebo groups were compared and no significant difference was found. There were no significant differences found between the two groups in the incidence of preterm delivery [RR=1.22, 95% CI (0.54-2.76), P=0.64], preeclampsia [RR=0.52, 95% CI (0.25-1.07), P=0.08], intrauterine growth restriction [RR=1.19, 95% CI (0.56-2.52), P=0.45] and thrombocytopenia [RR=1.17, 95% CI (0.09-14.42), P=0.90]. Conclusion This meta-analysis did not provide evidence that aspirin-heparin therapy had beneficial effect on un-explained recurrent miscarriage in terms of live birth rate, but it was relatively safe for it did not increase incidence of adverse pregnancy and adverse events. More well-designed and stratified double-blind RCT, individual-based meta-analysis regarding aspirin-heparin therapy are needed in future.

Key words: recurrent miscarriage, aspirin, heparin, randomized controlled trials, meta-analysis