Objective:To compare the effect of aspirin and enoxaparin on live births in women with unexplained recurrent miscarriages,as well as secondary outcomes including birth weight,uterine and umbilical blood flows,and congenital malformations. Design:Multicenter randomized comparative cohort study. Setting:Four centers including two university hospitals,a peripheral general hospital,and a community health clinic. Patient(s):One hundred seven patients were randomized,104 were available for analysis; 54 were randomized to enoxaparin and 50 to aspirin. Intervention(s):Treatment with enoxaparin or aspirin in subsequent pregnancy. Main Outcome Measure(s):Subsequent live births or miscarriage,and the incidence of obstetric complications. Result(s):Both groups had a similar live birth rate (relative risk = 0.92,95%confidence interval:0.58-1.46). In primary aborters,live births occurred in 17 of 18 (94%) enoxaparin-treated pregnancies compared to 18 of 22 (81%) aspirin-treated pregnancies. In the aspirin group,two pregnancies were terminated:for tricuspid insufficiency and for hemolysis,elevated liver enzymes,low platelet (HELLP) syndrome. One enoxaparin-treated infant was growth restricted (2,020 g) at 36 weeks. Preeclampsia was found in three aspirin-treated patients. Preterm delivery,placental Doppler blood flow,apgar scores,and mean birth weights were similar in both groups. In the aspirin group,one infant underwent orchidectomy after testicular torsion in utero,and one infant had hypoglycemia and convulsions. Conclusion(s):Both regimens were associated with a high live birth rate and few late pregnancy complications. Objective: To compare the effect of aspirin and enoxaparin on live births in women with unexplained recurrent miscarriages, as well as secondary outcomes including birth weight, uterine and umbilical blood flows, and congenital malformations. Design: Multicenter randomized comparative cohort study. Settings: Four Centers for two university hospitals, a peripheral general hospital, and a community health clinic. Patient (s): One hundred seven patients were randomized, 104 were available for analysis; 54 were randomized to enoxaparin and 50 to aspirin. Intervention (s): Treatment with enoxaparin or aspirin in subsequent pregnancy. Main Outcome Measure (s): Subsequent live births or miscarriage, and the incidence of obstetric complications. Result (s): Both groups had similar live birth rate (relative risk = 0.92, 95% Confirmation interval: 0.58-1.46) In primary aborters, live birth occurred in 17 of 18 (94%) enoxaparin-treated pregnancies compared to 18 of 22 (81%) aspirin-treated pregnancies. In the a The spirin group, two pregnancies were terminated: for tricuspid insufficiency and for hemolysis, elevated liver enzymes, low platelet (HELLP) syndrome. One enoxaparin-treated infant was restricted (2,020 g) at 36 weeks. Preeclampsia was found in three aspirin-treated Patients. Preterm delivery, placental Doppler blood flow, apgar scores, and mean birth weights were similar in both groups. In the aspirin group, one infant underwent orchidectomy after testicular torsion in utero, and one infant had hypoglycemia and convulsions. Conclusion (s) : Both regimens were associated with a high live birth rate and few late pregnancy complications.