Objective: Recurrent miscarriage is one of the most common clinical problems in reproduction. Many pathophysiological mechanisms postulated including hypercoagulability and immunological causes from undetectable autoantibodies. The current study aims to evaluate the effect of LMWH versus no heparin in treatment of women with recurrent miscarriage who were negatively tested for antiphosholipid antidodies.
Design: It is an open labeled randomized controlled trial.

Materials and Methods: Women who attend the outpatient Clinic in a University Hospital in Egypt and fulfilling the ACOG criteria of recurrent unexplained ptegnancy loss were approached for participation.
Eligible participants were randomly assigned into 2 groups. The study group includes 91 patients received LMWH ( Tinzaparin sodium 4500IU) subcutaneous daily injection with 500 micrograms folic acid once daily started once positive pregnancy test. The control group includes 59 patients received folic acid alone. The primary outcome ( upon which sample size estimated ) was the continuation of a viable pregnancy up to 20 weeks pregnancy.

Results: There was no significant difference between the study and the control groups as regard age, parity or socioeconomic level .There was a significant increase in the number of patients who continued beyond 20 weeks of gestation in the study group compared with the control 70.1% versus 54.5% , respectively (p=0.002) . The take home baby rate were also significantly higher in the heparin in the heparin group compared with the control group 65.7% versus 35.3%; respectively (p=0.001).

Conclusions: Early start of LMWH decrease the incidence of miscarriage in the first 20 weeks of pregnancy in patients with recurrent unexplained pregnancy loss negative for antiphospholipid antibodies.