Received October 23, 2019
Accepted April 30, 2020

Objective: To evaluate the efficacy and safety of low molecular weight heparin use in women with a history of recurrent abortion without an identified cause. Methods: Develop a systematic review to select the studies. Total found: 437 articles. Seven studies were completed or requested. The following variables were analyzed: clinical pregnancy, implantation rate, live births, abortion, premature birth, pregnancy, continuous pregnancy, beyond the 20th gestational week, congenital abnormality, hemorrhage, preeclampsia, placental premature detachment. Results: The LMWH group had a higher incidence of continuous pregnancy after the 20th week of gestation and there was no significant difference between the LMWH group and the expected management group in the analysis of other variables. Conclusions: No data were found to show risk and / or less use of LMWH compared to expected behavior, on the contrary, LMWH use increased the incidence of evolutionary pregnancy after the 20th gestational week, as well as the use of LMWH. LMWH has some influence on prophylactic treatment of repeat abortion for unknown cause.