Abstract： Objective To analyze the clinical characteristics of twin reversed arterial perfusion sequence (TRAP),and investigate its prenatal evaluation and clinical management.Methods Karyotype results and ultrasound data of 25 TRAP cases were retrospectively reviewed,including estimated weight and umbilical blood flow of acardiac twin,cardiac function and middle cerebral artery peak systolic velocity of pump twin.Various managements and the outcomes were analyzed.Results (1) Karyotype of amniotie fluid were tested in 16 pump twins.Mosaicism was found in 1 case (46,XX[36]/46,XY [14]).(2) According to the ultrasound evaluation,large acardia accounted for 87.0％ (20/23) cases.Abundant blood perfusion (inter-twin difference of umbilical resistance index ≤0.20) was indicated in 86.4％ (19/22) cases.Decompensation of cardiac function was suggested in 66.7％ (10/15) pump twins.Fetal anemia of pump twin indicated by middle cerebral artery peak systolic velocity＞1.5 multiples of the median was diagnosed in 75.0％ (12/16) cases.(3) The acardiac twin with abundant blood perfusion was more likely to be a large acardia than those without [94.7％(18/19) vs 1/3,Fisher exact test,P=0.04]; More pump twin with large acardia tended to have cardiac decompensation than non-large acardia pump twins [83.3 ％ (10/12) vs 0/3,Fisher exact test,P=0.02].(4) Eleven patients chose to terminate their pregnancies after being diagnosed.In 14 cases who continue the pregnancies,the survival rate of pump twin was 64.3％ (9/14).In 3 cases of non-large acardia without cardiac decompensation of pump twin,the patients selected conservative observation resulting in 2 term deliveries and 1 termination of pregnancy due to for exacerbation.Among 11 cases with large acardia,which the pump twins were complicated by cardiac decompensation or anemia,five cases selected conservative observation.One ended in spontaneous abortion; three exacerbated (one termination and two cesarean section before term with living births) ; one was stable until delivery.Another 6 cases received bipolar cord coagulation,and successful interruptions of acardiac blood flow were achieved in 5 cases among which 4 pump twins survived.Conclusions Prenatal diagnosis,cardiac function and fetal anemia of pump twin,together with the growth and blood supply of acardia are important indexes for prenatal evaluation of TRAP,on which our prompt management should be based.