Recent data indicates that 5 methyltetrahydrofolate (5MTHF) can reduce serum homocystein level more efficiently than folic acid. On the other hand, folic acid is currently an important part of treatment in idiopathic recurrent abortion. There is no study comparing the effectiveness of these supplements in the treatment of recurrent abortion. The aim of this study is to compare the efficiency of these two agents in the treatment of recurrent abortion. In this study, patients with idiopathic recurrent abortion, referring to Avicenna clinic will be randomly allocated into two groups of those taking either folic acid (5 mg) or 5 MTHF (5mg) from 8 weeks prior to conception until the 20th week of pregnancy. The serum level of folate, homocystein, and ongoing pregnancy will be analysed and compared in the two groups.