Objectives: to compare the efficacy and safety of the combination of unfractionated heparin  )UFH(  and Low Dose Aspirin (LDA)  with  that  of  low-molecular-weight heparin )LMWH(  and  LDA in  the  management  of  pregnant women with recurrent pregnancy loss secondary to antiphospholipid syndrome (APS). Methods : In a randomized prospective study, 60 women with a history of 3 or more consecutive spontaneous abortions and positive antiphospholipid antibodies were assigned in equal numbers to receive either UFH (5000 units, twice daily) plus LDA, or LMWH (enoxaparin 40 mg, once daily) plus LDA as soon as pregnancy was diagnosed. Results:  Twenty-four women in the LMWH group (80%) compared to 20 women in the UFH group (66.67%) delivered a viable infant (p >0.05). There was no significant difference in pregnancy complications or neonatal morbidity between the 2 groups. There were no incidences of excessive bleeding, thrombocytopenia, or osteoporotic fractures of excessive bleeding, thrombocytopenia, or osteoporotic fractures in either group. Conclusion: In this study, the use of LDA in combination with LMWH during pregnancy for the prevention of recurrent pregnancy loss in women with antiphospholipid syndrome seems to be as safe as UFH plus LDA. Large randomized trials will be required to determine differences in outcome with LMWH and LDA compared with treatment with UFH combined with LDA in this group of patients.